Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
Document and Entity Information - USD ($) $ in Thousands	Sep. 30, 2019	Nov. 30, 2019	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	MESA
Entity Registrant Name	MESA AIR GROUP INC
Entity Central Index Key	0000810332
Current Fiscal Year End Date	--09-30
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Public Float			$ 277,501,075
Entity Common Stock, Shares Outstanding		32,362,483
Entity File Number	001-38626
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	85-0302351
Entity Address, Address Line One	410 NORTH 44TH STREET
Entity Address, Address Line Two	SUITE 700
Entity Address, City or Town	PHOENIX
Entity Address, State or Province	AZ
Entity Address, Postal Zip Code	85008
City Area Code	602
Local Phone Number	685-4000
Document Annual Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, no par value
Documents Incorporated by Reference	Portions of the Registrant's definitive proxy statement relating to its 2020 annual meeting of shareholders are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. The 2020 Proxy Statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Current assets:
Cash and cash equivalents	$ 68,855	$ 103,311
Marketable securities	0	19,921
Restricted cash	3,646	3,823
Receivables, net	23,080	14,290
Expendable parts and supplies, net	21,337	15,658
Prepaid expenses and other current assets	40,923	40,914
Total current assets	157,841	197,917
Property and equipment, net	1,273,585	1,250,829
Intangibles, net	9,532	11,341
Lease and equipment deposits	2,167	2,598
Other assets	8,792	9,703
Total assets	1,451,917	1,472,388
Current liabilities:
Current portion of long-term debt and capital leases	165,900	155,170
Accounts payable ($1,729 and $1,330 to related party)	49,930	54,307
Accrued compensation	11,988	12,208
Other accrued expenses	28,888	29,696
Total current liabilities	256,706	251,381
Long-term debt and capital leases, excluding current portion	677,423	760,177
Deferred credits ($5,751 and $7,702 to related party)	12,134	15,393
Deferred income taxes	55,303	39,797
Other noncurrent liabilities	24,483	31,173
Total noncurrent liabilities	769,343	846,540
Total liabilities	1,026,049	1,097,921
Commitments and contingencies (Note 15 and Note 16)
Stockholders' equity:
Preferred stock of no par value, 5,000,000 shares authorized; no shares issued and outstanding
Common stock of no par value and additional paid-in capital, 125,000,000 shares authorized; 31,413,287 (2019) and 23,902,903 (2018) shares issued and outstanding, and 3,600,953 (2019) and 10,614,990 (2018) warrants issued and outstanding	238,504	234,683
Retained earnings	187,364	139,784
Total stockholders' equity	425,868	374,467
Total liabilities and stockholders' equity	$ 1,451,917	$ 1,472,388

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Statement Of Financial Position [Abstract]
Accounts payable to related party	$ 1,729	$ 1,330
Deferred credits to related party	$ 5,751	$ 7,702
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, no par value	$ 0	$ 0
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	31,413,287	23,902,903
Common stock, shares outstanding	31,413,287	23,902,903
Common stock, warrants issued	3,600,953	10,614,990
Common stock, warrants outstanding	3,600,953	10,614,990

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Operating revenues:
Total operating revenues	$ 723,357	$ 681,595	$ 643,576
Operating expenses:
Flight operations	210,879	209,065	155,516
Fuel	588	498	766
Maintenance	196,514	193,164	210,729
Aircraft rent	52,206	68,892	72,551
Aircraft and traffic servicing	3,972	3,541	3,676
General and administrative	50,527	53,647	38,996
Depreciation and amortization	77,994	65,031	61,048
Lease termination	9,540	15,109
Total operating expenses	602,220	608,947	543,282
Operating income	121,137	72,648	100,294
Other (expenses) income, net:
Interest expense	(55,717)	(56,867)	(46,110)
Interest income	1,501	114	32
Loss on extinguishment of debt	(3,616)
Other expense	(19)	(66)	(514)
Total other (expense), net	(57,851)	(56,819)	(46,592)
Income before taxes	63,286	15,829	53,702
Income tax expense (benefit)	15,706	(17,426)	20,874
Net income	$ 47,580	$ 33,255	$ 32,828
Net income per share
Basic	$ 1.37	$ 1.34	$ 1.41
Diluted	$ 1.36	$ 1.32	$ 1.40
Weighted-average common shares outstanding
Basic	34,764	24,826	23,201
Diluted	35,064	25,257	23,370
Contract Revenue [Member]
Operating revenues:
Total operating revenues	$ 682,834	$ 639,264	$ 618,698
Pass Through and Other [Member]
Operating revenues:
Total operating revenues	$ 40,523	$ 42,331	$ 24,878

Consolidated Statement of Stockholders Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Number of Warrants [Member]	Common Stock and Additional Paid-In Capital [Member]	Retained Earnings [Member]
Beginning balance at Sep. 30, 2016	$ 189,151			$ 114,211	$ 74,940
Beginning balance, shares at Sep. 30, 2016		10,369,643	13,150,610
Stock compensation expense	1,288			1,288
Repurchased shares and warrants	(1,043)			(1,043)
Repurchased shares and warrants, shares		(228,735)
Warrants converted to common stock		919,985	(919,985)
Restricted shares issued, shares		233,190
Net income	32,828				32,828
Ending balance at Sep. 30, 2017	222,224			114,456	107,768
Ending balance, shares at Sep. 30, 2017		11,294,083	12,230,625
Stock compensation expense	1,991			1,991
Repurchased shares and warrants	(7,709)	$ (5,000)		(7,709)
Repurchased shares and warrants, shares		(438,541)	(250,000)
Warrants converted to common stock		1,365,643	(1,365,643)
Restricted shares issued	11,918			11,918
Restricted shares issued, shares		1,327,700
Conversion of unvested restricted shares	2,321			2,321
IPO issuance	111,706			111,706
IPO issuance, shares		10,354,018	8
Cumulative effect of change in accounting principle	(1,239)				(1,239)
Net income	33,255				33,255
Ending balance at Sep. 30, 2018	374,467			234,683	139,784
Ending balance, shares at Sep. 30, 2018		23,902,903	10,614,990
Stock compensation expense	5,508			5,508
Stock issuance costs	185			185
Repurchased shares and warrants	(1,872)	$ (1,900)		(1,872)
Repurchased shares and warrants, shares		(205,235)
Warrants converted to common stock		7,014,037	(7,014,037)
Restricted shares issued, shares		701,582
Net income	47,580				47,580
Ending balance at Sep. 30, 2019	$ 425,868			$ 238,504	$ 187,364
Ending balance, shares at Sep. 30, 2019		31,413,287	3,600,953

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 47,580,000	$ 33,255,000	$ 32,828,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	77,994,000	65,031,000	61,048,000
Stock compensation expense	5,508,000	12,929,000	1,288,000
Deferred income taxes	15,503,000	(17,874,000)	20,515,000
Amortization of unfavorable lease liabilities and deferred credits	(10,839,000)	(11,035,000)	(10,626,000)
Amortization of debt financing costs and accretion of interest on non-interest-bearing subordinated notes	4,203,000	4,606,000	2,689,000
Loss on extinguishment of debt	3,616,000
(Gain)/loss on disposal of assets	(5,000)	307,000	533,000
Provision for obsolete expendable parts and supplies	642,000	200,000	419,000
Lease termination	9,540,000	15,109,000
Provision for doubtful accounts			(86,000)
Changes in assets and liabilities:
Receivables	(9,275,000)	(5,437,000)	530,000
Expendable parts and supplies	(6,310,000)	(744,000)	(3,379,000)
Prepaid expenses and other current assets	(713,000)	7,584,000	(17,243,000)
Accounts payable	12,119,000	2,427,000	(17,336,000)
Accrued liabilities	2,113,000	12,581,000	3,547,000
Net cash provided by operating activities	151,676,000	118,939,000	74,727,000
Cash flows used in investing activities:
Capital expenditures	(125,350,000)	(117,989,000)	(84,500,000)
Purchases of investment securities	(14,884,000)	(19,921,000)
Sales of investment securities	34,961,000
Proceeds from sale of rotable spare parts			18,000
Net returns (payments) of lease and equipment deposits	431,000	(653,000)	406,000
Net cash used in investing activities	(104,842,000)	(138,563,000)	(84,076,000)
Cash flows from financing activities:
Proceeds from long-term debt	171,658,000	187,703,000	185,912,000
Principal payments on long-term debt and capital leases	(244,087,000)	(222,153,000)	(152,995,000)
Debt financing costs	(5,680,000)	(5,852,000)	(3,377,000)
Debt prepayment costs	(1,672,000)
Proceeds from issuance of common stock		124,246,000
Stock issuance costs	185,000	(12,540,000)
Repurchase of stock	(1,871,000)	(4,993,000)	(1,043,000)
Net cash (used in) provided by financing activities	(81,467,000)	66,411,000	28,497,000
Net change in cash and cash equivalents	(34,633,000)	46,787,000	19,148,000
Cash and cash equivalents and restricted cash at beginning of period	107,134,000	60,347,000	41,199,000
Cash and cash equivalents and restricted cash at end of period	72,501,000	107,134,000	60,347,000
Supplemental cash flow information
Cash paid for interest	53,503,000	50,672,000	43,798,000
Cash paid for income taxes - net	419,000	385,000	332,000
Supplemental non-cash investing and financing activities
Accrued capital expenditures	$ 179,000	16,677,000	$ 9,533,000
Acquisition of capital leases		$ 10,473,000

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 68,855	$ 103,311	$ 56,788
Restricted cash	3,646	3,823	3,559
Cash, cash equivalents, and restricted cash in Consolidated Statement of Cash Flows	$ 72,501	$ 107,134	$ 60,347	$ 41,199

Organization and Operations

12 Months Ended

Sep. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Operations

1.	Organization and Operations

The Company

Mesa Air Group, Inc. ("Mesa" or the "Company") is a holding company whose principal subsidiary operates as a regional air carrier, providing scheduled passenger service. As of September 30, 2019, the Company served 125 cities in 39 states, the District of Columbia, Canada, Mexico and Cuba, and operated a fleet of 145 aircraft with approximately 730 daily departures.

The Company's airline operations are conducted by its regional airline subsidiary, Mesa Airlines, Inc. ("Mesa Airlines"), providing services to major air carriers under capacity purchase agreements. Mesa Airlines operates as American Eagle under a capacity purchase agreement with American Airlines, Inc. ("American") and as United Express under a capacity purchase agreement with United Airlines, Inc. ("United"). All of the Company's consolidated contract revenues for years ended September 30, 2019, 2018 and 2017 were derived from operations associated with these two capacity purchase agreements.

The financial arrangements between the Company and its major airline partners involve a revenue-guarantee arrangement (i.e. a "capacity purchase agreement") whereby the major airline pays a monthly guaranteed amount for each aircraft under contract, a fixed fee for each block hour and flight flown and reimbursement of certain direct operating expenses in exchange for providing regional flying. The major airline partners also pay certain expenses directly to suppliers, such as fuel, ground operations and certain landing fees. Under the terms of these capacity purchase agreements, the major airline controls route selection, pricing and seat inventories, thereby reducing the Company's exposure to fluctuations in passenger traffic, fare levels, and fuel prices.

On August 8, 2018, the Company filed its Second Amended and Restated Articles of Incorporation, which, among other things: (i) effected a 2.5-for-1 stock split of its common stock; and (ii) increased the authorized number of shares of its common and preferred stock to 125,000,000 and 5,000,000, respectively. All references to share and per share amounts in the Company's consolidated financial statements have been retrospectively revised to reflect the stock split and increase in authorized shares.

On August 14, 2018, the Company completed an initial public offering ("IPO") of its common stock, in which it issued and sold 9,630,000 shares (the "Firm Shares") of common stock at a public offering price of $12.00 per share, resulting in gross proceeds to the Company of approximately $115.6 million. Additionally, in connection with the IPO, the Company granted the underwriters an option to purchase up to an additional 1,444,500 shares of common stock at the same price. On September 11, 2018, the Company closed the sale of 1,344,500 shares ("Option Shares") of its common stock, in connection with the partial exercise of the overallotment option granted to the underwriters in its IPO. Of the 1,344,500 Option Shares sold, 723,985 were purchased directly from the Company and the remaining 620,515 shares were purchased directly from the selling shareholders. The Firm Shares and Option Shares were sold to the public for a price of $12.00 per share.

The sale of these shares raised gross proceeds of approximately $124,247,820. The Company did not receive any proceeds from the sale of the Option Shares by the selling shareholders.

As part of the IPO, stock appreciation rights ("SARs") previously issued under the Mesa Air Group, Inc. Amended and Restated Stock Appreciation Rights Plan (the "SAR Plan"), which settled only in cash, were cancelled and exchanged for an aggregate of 1,266,034 shares of restricted common stock under the Company's 2018 Equity Incentive Plan (the "2018 Plan") (see note 13 "Share-Based Compensation"), of which 966,022 were fully vested upon issuance and are included in the number of shares of common stock outstanding after the IPO. Of the 966,022 fully vested shares, 314,198 shares were retained by the Company to satisfy tax withholding obligations, resulting in a net issuance of 651,824 shares. Additionally, 983,113 shares of restricted common stock were issued to certain of its employees and directors under its 2018 Plan in exchange for the cancellation of 491,915 shares of existing unvested restricted phantom stock units and 491,198 shares of restricted stock under the 2011 and 2017 Plans, respectively.

American Capacity Purchase Agreement

As of September 30, 2019, the Company operated 62 CRJ-900 aircraft for American under a capacity purchase agreement. Unless otherwise extended or amended, the capacity purchase agreement for the aircraft expires between 2021 and 2025. In exchange for providing flights and all other services under the agreement, the Company receives a fixed monthly minimum amount per aircraft, plus certain additional amounts based upon the number of flights and block hours (the number of hours during which the aircraft is in revenue service, measured from the time of gate departure before take-off until the time of gate arrival at the destination) flown during the month. In addition, the Company may also receive incentives or pay penalties based upon the Company's operational performance, including controllable on-time departure and controllable completion percentages. American also reimburses the Company for the actual amount incurred for certain items such as passenger liability and hull insurance, and aircraft property taxes. In addition, American also provides, at no cost to the Company, certain ground handling and customer service functions, as well as airport-related facilities and fuel. The Company also receives a monthly profit margin payment from American based on the number of aircraft operating. The capacity purchase agreement is subject to early termination for cause under specified circumstances and subject to the Company's right to cure under certain conditions. American had a 7.1% and 7.2% ownership interest in the Company, calculated on a fully-diluted basis as of September 30, 2019 and 2018, respectively. The related party amounts presented on the consolidated balance sheets and statements of operations pertain to American.

On January 31, 2019, the Company entered into an amendment to the American Capacity Purchase Agreement, the terms of which provide for new and revised operational performance metrics, the Company's right to earn additional incentive compensation based on the achievement of such metrics, and the right of American to permanently withdraw up to six (6) aircraft in the event the Company fails to meet such new/revised performance metrics. Under the terms of such amendment the Company agreed, effective April 2, 2019, to convert two (2) aircraft to be utilized by the Company as operational spares in the Company's sole discretion throughout its system.

In July 2019, American exercised its right to permanently withdraw two (2) aircraft from the American Capacity Purchase Agreement due to the Company's failure to meet certain performance metrics. The aircraft were removed on November 2, 2019.

As of August 28, 2019, the Company had failed to meet certain performance metrics under the Term Sheet (the "August Failure"), which failure gave rise to American’s right to permanently withdraw two additional aircraft from the American CPA. In a separate agreement, American agreed to forbear from exercising its right to permanently withdraw these two aircraft. Under the terms of such forbearance, the Company and American agreed to reset the measurement period for certain performance metrics effective as of August 29, 2019. The parties also agreed that if the Company is out of compliance with applicable performance metrics on or after September 30, 2019, American retains the right to exercise its withdrawal rights for the August Failure by delivering 60 day prior written notice to the Company.

United Capacity Purchase Agreement

As of September 30, 2019, we operated 20 CRJ-700 and 60 E-175 aircraft for United under our United Capacity Purchase Agreement. In exchange for providing the flight services under our United Capacity Purchase Agreement, we receive a fixed monthly minimum amount per aircraft under contract plus certain additional amounts based upon the number of flights and block hours flown and the results of passenger satisfaction surveys. United also reimburses us for certain costs on an actual basis, including property tax per aircraft and passenger liability insurance. Other expenses, including fuel and certain landing fees, are directly paid to suppliers by United. We also receive a minimum profit margin based upon our operational performance. Under our United Capacity Purchase Agreement, United owns 42 of the 60 E-175 aircraft and leases them to us at nominal amounts. United reimburses us on a pass-through basis for all costs related to heavy airframe and engine maintenance, landing gear, auxiliary power units ("APUs") and component maintenance for the 42 E-175 aircraft owned by United.

Our United Capacity Purchase Agreement permits United, subject to certain conditions, including the payment of certain costs tied to aircraft type, to terminate the agreement in its discretion, or remove aircraft from service, by giving us notice of 90 days or more. In February 2018, we mutually agreed with United to temporarily remove two aircraft from service under our United Capacity Purchase Agreement. In July 2018, we were able to fully staff flight operations and these aircraft were placed back into service. During the temporary removal, we agreed to pay the lease costs associated with the two E-175 aircraft, which totaled $1.9 million as of September 30, 2018. If United elects to terminate our United Capacity Purchase Agreement in its entirety or permanently remove select aircraft from service, we are permitted to return any of the affected E-175 aircraft leased from United at no cost to us. In addition, if United removes any of our 18 owned E-175 aircraft from service at its direction, United would remain obligated to assume the aircraft ownership and associated debt with respect to such aircraft through the end of the term of the agreement.

On November 26, 2019, we amended and restated our United Capacity Purchase Agreement to, among other things, incorporate the terms of the 11 prior amendments to that Agreement and extend the term thereof through the addition of twenty (20) new Embraer E175LL aircraft to the scope of such Agreement. These new aircraft will be financed and owned by Mesa and operated for a period of twelve (12) years from the in-service date. Deliveries of the new E175LL aircraft are scheduled to begin in May 2020 and be completed by December 31, 2020. Commencing five (5) years after the actual in-service date, United has the right to remove the E175LL aircraft from service by giving us notice of 90 days or more, subject to certain conditions, including the payment of certain wind-down expenses plus, if removed prior to the ten (10) year anniversary of the in-service date, certain accelerated margin payments.

In addition to adding the 20 new E175LL aircraft to the amended and restated United Capacity Purchase Agreement, we extended the term of our 42 E-175 aircraft leased from United for an additional five (5) years, which now expire between 2024 and 2028. As part of the amended and restated United Capacity Purchase Agreement, we agreed to lease our twenty (20) CRJ-700 aircraft to another United Express service provider for a term of seven (7) years, with Mesa continuing to operate such aircraft until they are transitioned over the period between May 2020 and December 2020. In addition, we own 18 E-175 aircraft that expire in 2028. United has a right to purchase the CRJ 700 aircraft at the then fair market value.

The capacity purchase agreement is also subject to early termination for cause under specified circumstances and subject to the Company's right to cure under certain circumstances. United is also permitted, subject to certain conditions, to terminate the agreement early in its discretion by giving us notice of 90 days or more.

Summary of Significant Accounting Policies

12 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America ("GAAP") and include the accounts of the Company and its wholly owned operating subsidiaries. Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification ("ASC") and Accounting Standards Update ("ASU") of the Financial Accounting Standards Board ("FASB"). All intercompany accounts and transactions have been eliminated in consolidation.

The Company is an "emerging growth company," as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act") and may remain an emerging growth company until the last day of our fiscal year following the fifth anniversary of the IPO, subject to specified conditions. The JOBS Act provides that an emerging growth company can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to "opt out" of such extended transition period, which means that when a standard is issued or revised and it has different application dates for public or private companies, the Company will be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies.

Use of Estimates

The preparation of the Company's consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements. Actual results could differ from those estimates.

Segment Reporting

Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing operating performance. In consideration of ASC 280, "Segment Reporting," we are not organized around specific services or geographic regions. We currently operate in one service line providing scheduled flying services in accordance with our capacity purchase agreements.

While we operate under two separate capacity purchase agreements, we do not manage our business based on any performance measure at the individual contract level. Additionally, our chief operating decision maker uses consolidated financial information to evaluate our performance, which is the same basis on which he communicates our results and performance to our Board of Directors. He bases all significant decisions regarding the allocation of our resources on a consolidated basis. Based on the information described above and in accordance with the applicable literature, management has concluded that we are organized and operated as one operating and reportable segment.

All of our operating revenue in our 2019, 2018 and 2017 fiscal years was derived from operations associated with our American and United Capacity Purchase Agreements. It is currently impractical to provide certain information on our revenue from our customers for each of our services and geographic information on our revenues and long lived assets.

Cash and Cash Equivalents

The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.

Marketable Securities

The Company's investments in marketable securities are deemed by management to be available-for-sale and are reported at fair market value. The Company's holdings of marketable securities as of September 30, 2019 and 2018 was $0.0 million and $19.9, respectively.

Restricted Cash

Restricted cash primarily includes deposits in trust accounts to collateralize letters of credit and to fund workers' compensation claims, landing fees, and other business needs. Restricted cash is stated at cost, which approximates fair value.

The Company has an agreement with a financial institution for a $6.0 million letter of credit facility to issue letters of credit for landing fees, workers' compensation insurance, and other business needs. Pursuant to such agreement, $3.6 million and $3.8 million of outstanding letters of credit are required to be collateralized by amounts on deposit as of September 30, 2019 and 2018, respectively, which are classified as restricted cash.

Expendable Parts and Supplies

Expendable parts and supplies are stated at the lower of cost (using the first-in, first-out method) or market, and are charged to expense as they are used. The Company provides an allowance for obsolescence for such parts and supplies over the useful life of its aircraft after considering the useful life of each aircraft fleet, the estimated cost of expendable parts expected to be on hand at the end of the useful life, and the estimated salvage value of the parts. This allowance was $2.4 million and $1.8 million as of September 30, 2019 and 2018, respectively.

Prepaid Expenses

Prepaid expenses consist primarily of the excess of aircraft lease payments over the straight-lined lease expense. The straight-lined lease expense is net of estimated rebates to be received from the lessor during the term of the agreements, contingent on the Company performing certain engine restorations.

Property and Equipment

Property and equipment are stated at cost, net of manufacturer incentives, and depreciated over their estimated useful lives to their estimated salvage values, which are 20% for aircraft and rotable spare parts, using the straight-line method.

Estimated useful lives of the various classifications of property and equipment are as follows:

Property and Equipment		Estimated Useful Life
Buildings		30 years
Aircraft		25 years from manufacture date
Flight equipment		7-20 years
Equipment		5-9 years
Furniture and fixtures		3-5 years
Vehicles		5 years
Rotable spare parts		Life of the aircraft or term of the lease, whichever is less
Leasehold improvements		Life of the aircraft or term of the lease, whichever is less

Long-lived assets to be held and used are reviewed for impairment whenever events or changes in circumstances indicate that the related carrying amount may be impaired. The Company records an impairment loss if (i) the undiscounted future cash flows are found to be less than the carrying amount of the asset or asset group, and (ii) the carrying amount of the asset or asset group exceeds fair value. If an impairment loss has occurred, a charge is recorded to reduce the carrying amount of the asset to its estimated fair value. The Company recognized no impairment charges on property and equipment for the years ended September 30, 2019 and 2018.

Fair Value Measurements

The Company accounts for assets and liabilities in accordance with accounting standards that define fair value and establish a consistent framework for measuring fair value on either a recurring or a nonrecurring basis. Fair value is an exit price representing the amount that would be received to sell an asset, or paid to transfer a liability, in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability.

Accounting standards include disclosure requirements relating to the fair values used for certain financial instruments and establish a fair value hierarchy. The hierarchy prioritizes valuation inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of three levels:

▪

Level 1 – Observable inputs such as quoted prices in active markets;

▪

Level 2 – Inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and

▪

Level 3 – Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

Prepaid Maintenance Deposits

Prepaid maintenance deposits consist of payments made on a monthly basis to cover certain future maintenance events for leased flight equipment. The deposits are contractual obligations that are held in trust by the lessors. The deposits are only to be used to cover maintenance events, which include, among other things, C-checks, engine restoration events, engine life limited parts, landing gear repairs, and auxiliary power unit overhauls. The Company expenses the service as it is performed and receives reimbursement from the reserve trust account. The current portion is included in prepaid expenses and other current assets and the noncurrent portion is included in other assets on the consolidated balance sheet.

Debt Financing Costs

Debt financing costs consist of payments made to issue debt related to the purchase of aircraft, flight equipment, and certain flight equipment maintenance costs. The Company defers the costs and amortizes them over the term of the debt agreement. Debt financing costs related to a recognized debt liability are presented as a direct deduction from the carrying amount of the related long-term debt on the consolidated balance sheet. Debt financing costs with no related recognized debt liability are presented as assets, with the current portion included in prepaid expenses and other current assets and the noncurrent portion included in other assets on the consolidated balance sheet.

Unutilized Manufacturer Credits

Manufacturer credits received in connection with aircraft purchases that can be used for the future purchase of certain goods and services are recorded as a prepaid asset based on the value of the credits expected to be utilized, and the Company reduces the asset as the credits are utilized to fund such purchases. The current portion is included in prepaid expenses and other current assets and the noncurrent portion is included in other assets on the consolidated balance sheet.

Intangibles

Customer relationships are amortized using future discounted cash flows over the estimated life. In accordance with ASC 360, Property, Plant and Equipment, an intangible asset with a finite life that is being amortized is reviewed for impairment whenever events or changes in circumstances indicate that the related carrying amount may be impaired. The Company records an impairment loss if the undiscounted future cash flows are found to be less than the carrying amount of the asset and if the carrying amount of the asset exceeds fair value. If an impairment loss has occurred, a charge is recorded to reduce the carrying amount of the asset to its estimated fair value.

Other Assets

Other long-term assets primarily consist of noncurrent deferred reimbursed costs, debt financing costs, and prepaid maintenance deposits.

Income Taxes

Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in future years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company records deferred tax assets for the value of benefits expected to be realized from the utilization of alternative minimum tax credit carryforwards, capital loss carryforwards, and state and federal net operating loss carryforwards. The Company periodically reviews these assets to determine the likelihood of realization. To the extent the Company believes some portion of the benefit may not be realizable, an estimate of the unrealized position is made and a valuation allowance is recorded. The Company and its consolidated subsidiaries file a consolidated federal income tax return.

Other Noncurrent Liabilities

Other noncurrent liabilities consist of the remaining fair value adjustment for unfavorable aircraft operating leases related to a previous bankruptcy and related accounting. This adjustment to fair value is being amortized on a straight-line basis over the remaining initial lease terms for these aircraft. During each of the years ended September 30, 2019, 2018 and 2017, the Company recorded amortization of this unfavorable lease liability of $5.7 million, $6.6 million, and $6.8 million, respectively, as a reduction of lease expense. During the year ended September 30, 2019 and 2018, the Company wrote off $0.75 million and $1.2 million of unfavorable lease liability related to the lease termination of its aircraft lease facility with Wells Fargo Bank Northwest, National Association, as owner trustee and lessor (the "GECAS Lease Facility"), which was accounted for as lease termination expense.

Adoption of New Revenue Standard

On October 1, 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09" or "ASC 606") using the modified retrospective method. See Note 3: "Recent Accounting Pronouncements" in the notes to our consolidated financial statements for more information. To conform to ASC 606, the Company modified its revenue recognition policy as described below.

Revenue Recognition

The Company recognizes revenue when the service is provided under its capacity purchase agreements. Under these agreements, the major airline partners generally pay a fixed monthly minimum amount per aircraft, plus certain additional amounts based upon the number of flights and block hours flown. The contracts also include reimbursement of certain costs incurred by the Company in performing flight services. These costs, known as "pass-through costs," may include passenger and hull insurance as well as aircraft property taxes. Additionally, for the E-175 aircraft owned by United, the capacity purchase agreement provides that United will reimburse the Company for heavy airframe and engine maintenance, landing gear, APUs and component maintenance. The Company also receives compensation under its capacity purchase agreements for heavy maintenance expenses at a fixed hourly rate or per aircraft rate for all aircraft in scheduled service other than the E-175 aircraft owned by United. The contracts also include a profit margin on certain reimbursable costs, as well as a profit margin, incentives and penalties based on certain operational benchmarks. The Company is eligible to receive incentive compensation upon the achievement of certain performance criteria defined in the capacity purchase agreements. At the end of each period during the term of an agreement, the Company calculates the incentives achieved during that period and recognizes revenue attributable to the agreement during the period accordingly, subject to the variable constraint guidance under ASC 606. All revenue recognized under these contracts is presented as the gross amount billed to the major airline partners.

Under the capacity purchase agreements, the Company has committed to perform various activities that can be generally classified into in-flight services and maintenance services. When evaluating these services, the Company determined that the nature of its promise is to provide a single integrated service, flight services, because its contracts require integration and assumption of risk associated with both services to effectively deliver and provide the flights as scheduled over the contract term. Therefore, the in-flight services and maintenance services are inputs to that combined integrated flight service. Both the services occur over the term of the agreement and the performance of maintenance services significantly effects the utility of the in-flight services. The Company's individual flights flown under the capacity purchase agreements are deemed to be distinct and the flight service promised in the capacity purchase agreements represents a series of services that should be accounted for as a single performance obligation. This single performance obligation is satisfied over time as the flights are completed. Therefore, revenue is recognized when each flight is completed.

In allocating the transaction price, variable payments (i.e. billings based on flights and block hours flown, pass-through costs, etc.) that relate specifically to the Company's efforts in performing flight services are recognized in the period in which the individual flight is completed. The Company has concluded that allocating the variability directly to the individual flights results in an overall allocation meeting the objectives in ASC 606. This results in a pattern of revenue recognition that follows the variable amounts billed from the Company to their customers.

A portion of the Company's compensation under its capacity purchase agreements with American and United is designed to reimburse the Company for certain aircraft ownership costs. The Company has concluded that a component of its revenue under these agreements is deemed to be lease revenue, as such agreements identify the "right of use" of a specific type and number of aircraft over a stated period-of-time. The lease revenue associated with the Company's capacity purchase agreements is accounted for as an operating lease and is reflected as contract revenue on the Company's consolidated statements of operations.

The Company recognized $219.0 million, $217.0 million and $217.6 million of lease revenue for the twelve months ended September 30, 2019, 2018 and 2017, respectively. The Company has not separately stated aircraft rental income and aircraft rental expense in the condensed consolidated statements of operations because the use of the aircraft is not a separate activity of the total service provided.

The Company's capacity purchase agreements are renewable periodically and contain provisions pursuant to which the parties could terminate their respective agreements, subject to certain conditions as described in Note 1. The capacity purchase agreements also contain terms with respect to covered aircraft, services provided and compensation as described in Note 1. The capacity purchase agreements are amended from time to time to change, add or delete terms of the agreements.

The Company's revenues could be impacted by a number of factors, including amendment or termination of its capacity purchase agreements, contract modifications resulting from contract renegotiations, its ability to earn incentive payments contemplated under applicable agreements, and settlement of reimbursement disputes with the Company's major airline partners. In the event contracted rates are not finalized at a quarterly or annual financial statement date, the Company evaluates the enforceability of its contractual terms and when it has an enforceable right, it estimates the amount the Company expects to be entitled to that is subject to the ASC 606 constraint.

The Company's capacity purchase agreements contain an option that allows its major airline partners to assume the contractual responsibility for procuring and providing the fuel necessary to operate the flights that it operates for them. Both of the Company's major airline partners have exercised this option. Accordingly, the Company does not record an expense or revenue for fuel and related fueling costs for flying under its capacity purchase agreements. In addition, the Company's major airline partners also provide, at no cost to the Company, certain ground handling and customer service functions, as well as airport-related facilities and gates at their hubs and other cities. Services and facilities provided by the Company's major airline partners at no cost are presented net in its condensed consolidated financial statements; hence, no amounts are recorded for revenue or expense for these items.

Contract Liabilities

Contract liabilities consist of deferred credits for cost reimbursements from major airline partners related to aircraft modifications associated with capacity purchase agreements and pilot training. The deferred credits are recognized over time depicting the pattern of transfer of control of services resulting in ratable recognition of revenue over the remaining term of the capacity purchase agreements.

Current and non-current deferred credits are recorded to other accrued expenses and non-current deferred credits in the consolidated balance sheets. The Company's total current and non-current deferred credit balances at September 30, 2019, September 30, 2018 and September 30, 2017 are $12.1 million, $15.4 million and $17.2 million respectively. The Company recognized $5.1 million, $4.4 million and $3.8 million of the deferred credits to revenue in the consolidated statements of operations during the twelve months ended September 30, 2019, 2018 and 2017, respectively.

Contract Assets

The Company recognizes assets from the costs incurred to fulfill a contract including aircraft painting and reconfiguration and flight service personnel training costs. These costs are amortized based on the pattern of transfer of the services in relation to flight hours over the term of the contract. Contract assets are recorded as other assets in the consolidated balance sheets. The Company's contract assets balances at September 30, 2019, September 30, 2018 and September 30, 2017 are $3.9 million, $4.6 million and $6.1 million, respectively. Contract cost amortization was $2.4 million, $1.9 million and $1.6 million for the twelve months ended September 30, 2019, 2018 and 2017, respectively.

Maintenance Expense

The Company operates under an FAA approved continuous inspection and maintenance program. The Company uses the direct expense method of accounting for its maintenance of regional jet engine overhauls, airframe, landing gear, and normal recurring maintenance wherein the expense is recognized when the maintenance work is completed, or over the period of repair, if materially different. Our maintenance policy is determined by fleet when major maintenance is incurred. For leased aircraft, the Company is subject to lease return provisions that require a minimum portion of the "life" of an overhaul be remaining on the engine at the lease return date. The Company estimates the cost of maintenance lease return obligations and accrues such costs over the remaining lease term when the expense is probable and can be reasonably estimated.

Under the Company's aircraft operating lease agreements and FAA operating regulations, it is obligated to perform all required maintenance activities on its fleet, including component repairs, scheduled air frame checks and major engine restoration events. The Company estimates the timing of the next major maintenance event based on assumptions including estimated usage, FAA-mandated maintenance intervals and average removal times as recommended by the manufacturer. The timing and the cost of maintenance are based on estimates, which can be impacted by changes in utilization of its aircraft, changes in government regulations and suggested manufacturer maintenance intervals. Major maintenance events consist of overhauls to major components.

Engine overhaul expense totaled $30.0 million, $51.2 million and $64.0 million for the years ended September 30, 2019, 2018 and 2017, respectively, of which $6.0 million, $12.3 million and $0.3 million was pass-through expense. Airframe check expense totaled $17.2 million, $21.5 million and $22.6 million for the years ended September 30, 2019, 2018 and 2017, respectively, of which $0.4 million, $7.5 million and $4.9 million was pass-through expense.

Pursuant to the United capacity purchase agreement, United reimburses the Company for heavy maintenance on certain E-175 aircraft. Those reimbursements are included in pass-through and other revenue. See Note 1: "Organization and Operations" for further information.

Aircraft Leases

In addition to the aircraft we receive from United under our Capacity Purchase Agreement, approximately 12% of our aircraft are leased from third parties. In order to determine the proper classification of a lease as either an operating lease or a capital lease, we must make certain estimates at the inception of the lease relating to the economic useful life and the fair value of an asset as well as select an appropriate discount rate to be used in discounting future lease payments. These estimates are utilized by management in making computations as required by existing accounting standards that determine whether the lease is classified as an operating lease or a capital lease. All of our aircraft leases have been classified as operating leases, which results in rental payments being charged to expense over the term of the related leases. Additionally, operating leases are not reflected in our consolidated balance sheets and accordingly, neither a lease asset nor an obligation for future lease payments is reflected in our consolidated balance sheets. In the event that we or one of our major airline partners decide to exit an activity involving leased aircraft, losses may be incurred. In the event that we exit an activity that results in exit losses, these losses are accrued as each aircraft is removed from operations for early termination penalties, lease settle up and other charges. See Note 3: "Recent Accounting Pronouncements" in the notes to our consolidated financial statements below for a discussion of a new accounting standard that is likely to have an impact on our aircraft lease accounting beginning in fiscal year 2020.

Change in Accounting Policy

Stock Appreciation Rights ("SARs") and Phantom Stock historically were accounted for as liability compensatory awards under ASC 710, Compensation – General, valued using the intrinsic value method, as permitted by ASC 718, Compensation – Stock Compensation, for nonpublic entities. Upon becoming a public company, as defined in ASC 718, in the third quarter of fiscal 2018, the Company was required to change its methodology for valuing the SARs and Phantom Stock. The SARs and Phantom Stock were re-measured at each quarterly reporting date and were accounted for prospectively at fair value using a Black-Scholes fair value pricing model until they were converted to restricted stock awards upon completion of the Company's IPO. The Company recorded the impact of the change in valuation methods as a cumulative effect of a change in accounting principle, as permitted by ASC 250, Accounting Changes and Error Corrections. The effect of the change increased the SARs and Phantom Stock liability by $2.4 million which was the difference in compensation cost measured using the intrinsic value method and the fair value method. An equal and offsetting change to retained earnings in the consolidated balance sheet was recorded with the revaluation. Any future changes in fair value were recorded as compensation expense in the consolidated statement of operations. Upon completion of the Company's IPO the SARs and Phantom Stock were cancelled and exchanged for shares of restricted stock under our 2018 Plan.

Recent Accounting Pronouncements

12 Months Ended

Sep. 30, 2019

Accounting Changes And Error Corrections [Abstract]

Recent Accounting Pronouncements

3.	Recent Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). ASC 606 establishes a new recognition model that requires revenue to be recognized in a manner to depict the transfer of goods or services to a customer at an amount that reflects the consideration expected to be entitled in exchange for those goods or services. On October 1, 2018, the Company adopted this ASU using the modified retrospective method. Under the new standard, the Company concluded that, in addition to the aircraft lease, the individual flights are distinct services and the flight services promised in the capacity purchase agreements represent a series of services that should be accounted for as a single performance obligation. Revenue is recognized over time as the flights are completed. The adoption of this ASU did not have an impact on recorded amounts when applied to the opening balance sheet as of October 1, 2018. The adoption did not impact the condensed consolidated financial statements presented other than the disclosures noted in Note 2: "Summary of Significant Accounting Policies."

In August 2014, The FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern: Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern (Topic 205), which provides guidance on determining when and how to disclose going-concern uncertainties in the consolidated financial statements. The new standard requires management to perform interim and annual assessments of an entity's ability to continue as a going concern within one year of the date the consolidated financial statements are issued. An entity must provide certain disclosure if "conditions or events raise substantial doubt about the entity's ability to continue as a going concern." The update applies to all entities and is effective for annual periods ending after December 15, 2016, and interim periods thereafter. The Company adopted this ASU in fiscal year 2018, and the adoption did not have a material impact on the consolidated financial statements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) ("ASU 2016-02"), which provides guidance requiring lessees to recognize a right-of-use asset and a lease liability on the balance sheet for substantially all leases, with the exception of short-term leases. Leases will be classified as either financing or operating, with classification affecting the pattern of expense recognition in the statement of income. The guidance is effective for annual periods beginning after December 15, 2018, with early adoption permitted.

Based on the Company's initial assessment, the adoption of Topic 842 will significantly increase the Company's assets and liabilities primarily to reflect its aircraft operating lease liability and related right-of-use asset. As of September 30, 2019, the Company had 18 leased aircraft under operating leases in its fleet. The Company also has leases for a nominal fee for 42 aircraft owned by United, spare engines and other real estate leases. The Company does not expect the adoption of the New Lease Standard to impact any of its existing debt covenants. Additionally, the Company does not expect the adoption to have a significant impact on the recognition, measurement or presentation of lease revenue and lease expenses within the consolidated statements of operations or the consolidated statements of cash flows. The Company does not anticipate the adoption of Topic 842 will have a material impact on the timing or amount of the Company's lease revenue as a lessor. The Company will adopt Topic 842 on October 1, 2019.

The Company expects to elect several of the practical expedients available under the transition provisions of Topic 842, including (i) not reassessing whether expired or existing contracts contain leases, (ii) lease classification, and (iii) not revaluing initial direct costs for existing leases. The Company plans to elect the practical expedient which will allow aggregation of non-lease components with the related lease components when evaluating accounting treatment. Also, the Company plans to not apply Topic 842 to leases that, at the commencement date, have a lease term of 12 months or less and do not include an option to purchase the underlying asset that the Company is reasonably certain to exercise. Lastly, the Company currently plans to apply the modified retrospective adoption method, utilizing the simplified transition option available in Topic 842, which allows entities to continue to apply the legacy guidance in ASC 840, including its disclosure requirements, in the comparative periods presented in the year of adoption.

Upon adoption, the Company anticipates it will reflect a lease liability in the range of $130 to $170 million and a right-of-use asset of $120 to $180 million. Upon adoption, the right-of-use asset is expected to include prepaid aircraft rents, accrued aircraft rents and deferred rent credits that were separately stated in the Company's September 30, 2019 balance sheet. These estimates are subject to revision based upon the Company's adoption of Topic 842 in fiscal year 2020.

In March of 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09"). With this standard, all excess tax benefits and tax deficiencies are required to be recognized as income tax benefit or expense in the income statement. The tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur. An entity also should recognize excess tax benefits regardless of whether the benefit reduces taxes payable in the current period. ASU 2016-09 is effective for annual periods beginning after December 15, 2016, and interim periods within those annual periods. The Company adopted ASU 2016-09 in the first quarter of the year ended September 30, 2018. This change in accounting principle has been applied on a modified retrospective transition method by means of a cumulative effect adjustment to equity as of the beginning of fiscal year 2018 as a cumulative-effect adjustment increasing deferred tax assets by $0.4 million, increasing income tax expense by $0.3 million, and increasing retained earnings by $0.7 million. Adoption of ASU 2016-09 did not have any other material effect on the Company's results of operations, financial position or cash flows.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (a consensus of the FASB Emerging Issues Task Force), which clarifies how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The new standard is effective for fiscal years beginning after December 15, 2017, with early adoption permitted. The Company adopted the standard effective October 1, 2018; the adoption of this standard did not have a material impact on the financial statements.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force), that requires restricted cash and cash equivalents to be included with cash and cash equivalents on the statement of cash flows. The new standard is effective for fiscal years beginning after December 15, 2017, with early adoption permitted. The Company adopted the standard effective October 1, 2018 and modified the presentation to include changes in restricted cash in the Company's Consolidated Statement of Cash Flows.

Concentrations

12 Months Ended

Sep. 30, 2019

Risks And Uncertainties [Abstract]

Concentrations

4.	Concentrations

At September 30, 2019, the Company had capacity purchase agreements with American and United. All of the Company's consolidated revenue for the years ended September 30, 2019, 2018 and 2017 and accounts receivable at the end of September 30, 2019 and 2018 was derived from these agreements. The terms of both the American and United capacity purchase agreements are not aligned with the lease obligations on the aircraft performing services under such agreements. As of September 30, 2019, we had 17 aircraft with leases extending past the term of their corresponding capacity purchase agreements which results in a significant amount of an aggregate exposure and no financing arrangements with projected negativity. We intend to continue to align the terms of our aircraft leases and financing agreements with the terms of our capacity purchase agreements in order to maintain low "tail risk."

Amounts billed by the Company under capacity purchase agreements are subject to the Company's interpretation of the applicable capacity purchase agreement and are subject to audit by the Company's major airline partners. Periodically, the Company's major airline partners dispute amounts billed and pay amounts less than the amount billed. Ultimate collection of the remaining amounts not only depends upon the Company prevailing under the applicable audit, but also upon the financial well-being of the major airline partner. As such, the Company periodically reviews amounts past due and records a reserve for amounts estimated to be uncollectible. The allowance for doubtful accounts was $1.0 million and $1.3 million at September 30, 2019 and 2018, respectively. If the Company's ability to collect these receivables and the financial viability of our partners is materially different than estimated, the Company's estimate of the allowance could be materially impacted.

American accounted for approximately 53%, 54% and 56% of the Company's total revenue for the years ended September 30, 2019, 2018 and 2017, respectively. United accounted for approximately 47%, 46% and 44% of the Company's total revenue for the years ended September 30, 2019, 2018 and 2017, respectively. A termination of either the American or the United capacity purchase agreement would have a material adverse effect on the Company's business prospects, financial condition, results of operations, and cash flows.

Balance Sheet Information

12 Months Ended

Sep. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Information

6.	Balance Sheet Information

Certain significant amounts included in the Company's consolidated balance sheet as of September 30, 2019 and 2018, consisted of the following (in thousands):

	September 30,			September 30,
	2019			2018
Expendable parts and supplies, net
Expendable parts and supplies	$	25,336		$	18,907
Less obsolescence and other		(3,999	)		(3,249	)
	$	21,337		$	15,658
Prepaid expenses and other current assets
Prepaid aircraft rent	$	35,786		$	30,267
Unutilized manufacturer credits		—			4,500
Deferred offering and reimbursed costs		2,092			1,945
Other		3,045			4,202
	$	40,923		$	40,914
Property and equipment—net
Aircraft and other flight equipment substantially pledged	$	1,582,199		$	1,502,940
Other equipment		5,122			3,721
Leasehold improvements		2,797			2,754
Vehicles		924			692
Building		699			699
Furniture and fixtures		302			287
Total property and equipment		1,592,043			1,511,093
Less accumulated depreciation		(318,458	)		(260,264	)
	$	1,273,585		$	1,250,829
Other accrued expenses
Accrued property taxes	$	9,186		$	6,981
Accrued interest		4,497			6,118
Accrued vacation		6,128			5,470
Accrued wheels, brakes and tires		1,513			1,452
Other		7,564			9,675
	$	28,888		$	29,696

Depreciation expense totaled $76.2 million, $64.6 million and $60.7 million for the years ended September 30, 2019, 2018 and 2017, respectively.

The Company recorded amortization of the unfavorable lease liability amounting to $5.7 million, $6.6 million and $6.8 million for the years ended September 30, 2019, 2018 and 2017, respectively, as a reduction to lease expense. During the year ended September 30, 2019 and 2018 the Company wrote off $0.8 million and $1.2 million of unfavorable lease liability related to the lease termination of its aircraft lease facility with Wells Fargo Bank Northwest, National Association, as owner trustee and lessor (the "GECAS Lease Facility"), which was accounted for as lease termination expense.

Fair Value Measurements

12 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

7.	Fair Value Measurements

The Company did not measure any of its assets or liabilities at fair value on a recurring or nonrecurring basis as of September 30, 2019 and 2018.

The carrying values of cash and cash equivalents, accounts receivable, and accounts payable included on the consolidated balance sheets approximated fair value at September 30, 2019 and 2018.

The Company's debt agreements are not traded on an active market. The Company has determined the estimated fair value of its debt to be Level 3, as certain inputs used to determine the fair value of these agreements are unobservable and, therefore, could be sensitive to changes in inputs. The Company utilizes the discounted cash flow method to estimate the fair value of Level 3 debt.

The carrying value and estimated fair value of the Company's long-term debt, including current maturities, were as follows (in millions):

	September 30, 2019				September 30, 2018
	Carrying		Fair		Carrying		Fair
	Value		Value		Value		Value
Long-term debt, including current maturities⁽¹⁾	$	858.1	$	882.7	$	930.2	$	926.2

⁽¹⁾	Current and prior period long-term debts' carrying and fair values exclude net debt issuance costs.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Long-Term Debt and Other Borrowings

12 Months Ended

Sep. 30, 2019

Debt Disclosure [Abstract]

Long-Term Debt and Other Borrowings

8.	Long-Term Debt and Other Borrowings

Long-term debt as of September 30, 2019 and 2018, consisted of the following (in thousands):

	September 30,			September 30,
	2019			2018
Notes payable to financial institution, collateralized by the underlying aircraft, due 2019⁽¹⁾⁽²⁾	$	—		$	4,428
Notes payable to financial institution, collateralized by the underlying aircraft, due 2022⁽³⁾⁽⁴⁾		49,795			69,340
Notes payable to financial institution, collateralized by the underlying aircraft, due 2024⁽⁵⁾		60,761			72,438
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2027⁽⁶⁾		110,912			122,591
Notes payable to secured parties, collateralized by the underlying aircraft, due 2028⁽⁷⁾		191,168			209,240
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2028⁽⁸⁾		152,945			167,269
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2022⁽¹⁶⁾		71,998			95,060
Notes payable to financial institution, collateralized by the underlying equipment, due 2022⁽⁹⁾		—			88,162
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2022⁽¹⁰⁾		47,309			63,403
Notes payable to financial institution, collateralized by the underlying equipment, due 2020⁽¹¹⁾		1,659			3,318
Notes payable to financial institution due 2020⁽¹²⁾		2,329			4,360
Notes payable to financial institution, collateralized by the underlying equipment, due 2020⁽¹³⁾		6,962			14,971
Notes payable to financial institution due 2019⁽¹⁴⁾		—			5,896
Other obligations due to financial institution, collateralized by the underlying equipment, due 2023⁽¹⁵⁾		8,530			9,731
Notes payable to financial institution, collateralized by the underlying equipment, due 2024⁽¹⁷⁾		80,153			—
Notes payable to financial institution, collateralized by the underlying aircraft, due 2023⁽¹⁸⁾		65,625			—
Notes payable to financial institution due 2023 ⁽¹⁹⁾		8,000			—
Total long-term debt		858,145			930,207
Less current portion		(165,900	)		(155,170	)
Less unamortized debt issuance costs		(14,822	)		(14,860	)

Long-term debt—excluding current portion	$	677,423		$	760,177

⁽¹⁾	In fiscal 2005, the Company financed five CRJ-900 aircraft with $118 million in debt. The debt bears interest at the monthly London InterBank Offered Rate ("LIBOR"), plus 3% and requires monthly principal and interest payments. As of September 30, 2019, the loan has been repaid.

⁽²⁾	In fiscal 2004, the Company financed five CRJ-700 and nine CRJ 900 aircraft with $254.7 million in debt. The debt bears interest at the monthly LIBOR plus 3% and requires monthly principal and interest payments. As of September 30, 2019, the loan has been repaid.

⁽³⁾	In fiscal 2007, the Company financed three CRJ-900 and three CRJ-700 aircraft for $120.3 million. The debt bears interest at the monthly LIBOR plus 2.25% (4.270% at September 30, 2019) and requires monthly principal and interest payments.

⁽⁴⁾	In fiscal 2014, the Company financed 10 CRJ-900 aircraft for $88.4 million. The debt bears interest at the monthly LIBOR plus a spread ranging from 1.95% to 7.25% (3.970% to 9.270% at September 30, 2019) and requires monthly principal and interest payments.

⁽⁵⁾	In fiscal 2014, the Company financed eight CRJ-900 aircraft with $114.5 million in debt. The debt bears interest at 5% and requires monthly principal and interest payments.

⁽⁶⁾

In fiscal 2015, the Company financed seven CRJ-900 aircraft with $170.2 million in debt. The senior notes payable of $151 million bear interest at monthly LIBOR plus 2.71% (4.730% at September 30, 2019) and require monthly principal and interest payments. The subordinated notes payable are noninterest-bearing and become payable in full on the last day of the term of the notes. The Company has imputed an interest rate of 6.25% on the subordinated notes payable and recorded a related discount of $8.1 million, which is being accreted to interest expense over the term of the notes.

⁽⁷⁾	In fiscal 2017, the Company financed 10 E-175 aircraft with $246 million in debt under an EETC financing arrangement (see discussion below). The debt bears interest ranging from 4.75% to 6.25% and requires semi-annual principal and interest payments.

⁽⁸⁾

In fiscal 2017, the Company financed eight E-175 aircraft with $195.3 million in debt. The senior notes payable of $172 million bear interest at the three-month LIBOR plus a spread ranging from 2.20% to 2.32% (4.290% to 4.410% at September 30, 2019) and require quarterly principal and interest payments. The subordinated notes payable bear interest at 4.50% and require quarterly principal and interest payments.

⁽⁹⁾	In fiscal 2018, the Company financed certain flight equipment with $99.1 million in debt. The debt bears interest at the monthly LIBOR (rounded to the nearest 16th) plus 7.25% and requires monthly principal and interest payments. As of September 30, 2019, the loan has been repaid.

⁽¹⁰⁾

In December 2017, the Company refinanced nine CRJ-900 aircraft with $74.9 million in debt. The senior notes payable of $46.9 million bear interest at the three-month LIBOR plus 3.50% (5.590% at September 30, 2019) and require quarterly principal and interest payments. The subordinated notes payable bear interest at the three-month LIBOR plus 4.50% (6.590% at September 30, 2019) and require quarterly principal and interest payments.

⁽¹¹⁾	In fiscal 2015, the Company financed certain flight equipment with $8.3 million in debt. The debt bears interest at 5.163% and requires monthly principal and interest payments.

⁽¹²⁾	In fiscal 2015 and 2017, the Company financed certain flight equipment maintenance costs with $10.2 million in debt. The debt bears interest at the three-month LIBOR plus 3.07% (5.160% at September 30, 2019) and requires quarterly principal and interest payments.

⁽¹³⁾

In fiscal 2017 and 2018, the Company financed certain flight equipment maintenance costs with $11.9 million in debt. The debt bears interest at the three-month LIBOR plus a spread ranging from 2.93% to 2.96% (5.020% to 5.050% at September 30, 2019) and requires quarterly principal and interest payments. The debt is subject to a fixed charge ratio covenant. As of September 30, 2019, the Company was in compliance with this covenant.

⁽¹⁴⁾

In fiscal 2018, the Company financed certain flight equipment maintenance costs with $25.0 million in debt. The debt bears interest at the three-month LIBOR plus 3.30% and requires quarterly principal and interest payments. The debt is subject to a fixed charge ratio covenant. As of September 30, 2019, the loan has been repaid.

⁽¹⁵⁾	In February 2018, the Company leased two spare engines. The leases were determined to be capital as the leases contain a bargain purchase option at the end of the term. Imputed interest is 9.128% and the leases requires monthly payments.

⁽¹⁶⁾

In June 2018, the Company refinanced six CRJ-900 aircraft with $27.5 million in debt and financed nine CRJ-900 aircraft, which were previously leased, with $69.6 million in debt. The senior notes payable of $65.8 million bear interest at the three-month LIBOR plus 3.50% (5.590% at September 30, 2019) and require quarterly principal and interest payments. The subordinated notes payable of $29.8 million bear interest at three-month LIBOR plus 7.50% (9.590% at September 30, 2019) and require quarterly principal and interest payments.

⁽¹⁷⁾	In January 2019, the Company financed certain flight equipment with $91.2 million in debt. The debt bears interest at the monthly LIBOR plus 3.10% (5.120% at September 30, 2019) and requires monthly principal and interest payments.

⁽¹⁸⁾	In June 2019, the Company financed ten CRJ-700 aircraft with $70.0 million in debt, which were previously leased. The debt bears interest at the monthly LIBOR plus 5.25% (7.270% at September 30, 2019) and requires monthly principal and interest payments.

⁽¹⁹⁾

The Company financed certain flight equipment on September 27, 2019 for $8.0 million. The debt bears interest at the monthly LIBOR plus 5.25% (7.27% at September 30, 2019) and requires monthly principal and interest payments. As of September 30, 2019 we had $8.0 million outstanding under these notes.

Principal maturities of long-term debt as of September 30, 2019, and for each of the next five years are as follows (in thousands):

	Total Principal
Periods Ending September 30,	Amount
2020		165,900
2021		161,359
2022		152,745
2023		103,165
2024		71,033
Thereafter		203,943
	$	858,145

The net book value of collateralized aircraft and equipment as of September 30, 2019 was $1,203.5 million.

In December 2015, an Enhanced Equipment Trust Certificate ("EETC") pass-through trust was created to issue pass-through certificates to obtain financing for new E-175 aircraft. At September 30, 2019, Mesa has $191.2 million of equipment notes outstanding issued under the EETC financing included in long-term debt on the consolidated balance sheets. The structure of the EETC financing consists of a pass-through trust created by Mesa to issue pass-through certificates, which represent fractional undivided interests in the pass-through trust and are not obligations of Mesa.

The proceeds of the issuance of the pass-through certificates were used to purchase equipment notes which were issued by Mesa and secured by its aircraft. The payment obligations under the equipment notes are those of Mesa. Proceeds received from the sale of pass-through certificates were initially held by a depositary in escrow for the benefit of the certificate holders until Mesa issued equipment notes to the trust, which purchased such notes with a portion of the escrowed funds.

Mesa evaluated whether the pass-through trust formed for its EETC financing is a Variable Interest Entity ("VIE") and required to be consolidated. The pass-through trust was determined to be a VIE, however, the Company has determined that it does not have a variable interest in the pass-through trust, and therefore, has not consolidated the pass-through trust with its financial statements.

On June 27, 2018, the Company refinanced $16.0 million of debt on six CRJ-900 aircraft (due in 2019), with $27.5 million of debt, resulting in net cash proceeds to the Company of $10.4 million after transaction related fees. The notes payable require quarterly payments of principal and interest through fiscal 2022 bearing interest at LIBOR plus 3.50%.

On June 28, 2018, the Company purchased nine CRJ-900 aircraft, which were previously leased under the GECAS Lease Facility, for $76.5 million. The Company financed the aircraft purchase with $69.6 million in new debt and proceeds from the June 2018 refinancing of six CRJ-900 aircraft. The notes payable of $69.6 million require quarterly payments of principal and interest through fiscal 2022 bearing interest at LIBOR plus a spread ranging from 3.50% for the senior promissory notes to 7.50% for the subordinated promissory notes. The Company recorded non-cash lease termination expense of $15.1 million in connection with the lease buyout. Also, as part of the transaction, the Company (i) received $4.5 million of future goods and services credits and $5.6 million of loan forgiveness for loans with a maturity date in 2027 from the aircraft manufacturer, and (ii) mutually agreed with GE Capital Aviation Services LLC to terminate the GE Warrant to purchase 250,000 shares of common stock.

On January 28, 2019, the Company entered into a Term Loan Agreement (the "Term Loan") pursuant to which the lenders thereunder lent the Company term loans in the aggregate principal amount of $91.2 million. Borrowings under the Term Loan bear interest at LIBOR plus 3.10%. This interest rate is significantly lower than the interest rate under the Company's Spare Engine Facility (defined above), which the Term Loan refinanced and replaced. The Spare Engine Facility accrued interest at LIBOR plus 7.25%. The Term Loan has a term of five years, with principal and interest payments due monthly over the term of the loan in accordance with an amortization schedule. The Company recorded a loss on extinguishment of debt of $3.6 million, due to a $1.9 million write-off of financing fees and $1.7 million in prepayment penalties, in connection with the repayment of the Spare Engine Facility.

On June 14, 2019, the Company completed the purchase of ten CRJ-700 aircraft, which were previously leased under the GECAS Lease Facility, for $70.0 million. The Company financed the aircraft purchase with $70.0 million in new debt. The notes payable of $70.0 million require monthly payments of principal and interest through fiscal 2023 bearing interest at LIBOR plus 5.25%. The Company recorded non-cash lease termination expense of $9.5 million in connection with the lease buyout.

On September 25, 2019, the company extended the term on their $35 million working capital draw loan by three years, which now terminates in September 2022. Interest is assessed on drawn amounts at one-month LIBOR plus 3.75%.

On September 27, 2019, the company financed certain flight equipment for $8.0 million in new debt. The debt of $8.0 million require monthly payments of principal and interest through fiscal 2023 bearing interest at Libor plus 5.25%.

Earnings Per Share

12 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Earnings Per Share

9.	Earnings Per Share

Calculations of net income per common share were as follows (in thousands, except per share data):

	Year Ended September 30,
	2019		2018		2017
Net income	$	47,580	$	33,255	$	32,828
Basic weighted average common shares outstanding		34,764		24,826		23,201
Add: Incremental shares for:
Dilutive effect of warrants		—		116		93
Dilutive effect of restricted stock		300		315		76
Diluted weighted average common shares outstanding		35,064		25,257		23,370

Net income per common share
Basic	$	1.37	$	1.34	$	1.41
Diluted	$	1.36	$	1.32	$	1.40

Basic income per common share is computed by dividing net income attributable to Mesa Air Group by the weighted average number of common shares outstanding during the period.

The number of incremental shares from the assumed issuance of shares relating to restricted stock and exercise of warrants (excluding warrants with a nominal conversion price) is calculated by applying the treasury stock method. Share-based awards and warrants whose impact is considered to be anti-dilutive under the treasury stock method were excluded from the diluted net income or loss per share calculation. In loss periods, these incremental shares are excluded from the calculation of diluted loss per share, as the inclusion of unvested restricted stock and warrants would have an anti-dilutive effect. There were no anti-dilutive shares relating to restricted stock and exercise of warrants that were excluded from the calculation of diluted loss per share for the years ended September 30, 2019, 2018 and 2017.

Restatement

12 Months Ended

Sep. 30, 2019

Accounting Changes And Error Corrections [Abstract]

Restatement

10.	Restatement

Basic and Diluted Net Income per Common Share Available to Common Shareholders:

Subsequent to the issuance of the Company's consolidated financial statements for the year ended September 30, 2018, we determined our previously issued consolidated financial statements included warrants with a nominal conversion price in diluted income per common share available to common shareholders, however, they should have been included in basic income per common share available to common shareholders. As a result, basic income per common share available to common shareholders for the years ended September 30, 2018 and 2017 have been restated to appropriately include the warrants with a nominal conversion price in basic income per common share available to common shareholders. Since diluted shares are under the treasury stock method, diluted common share available to common shareholders were impacted by this change and have been restated.

The restatement adjustment did not impact our previously reported consolidated balance sheet, consolidated statements of stockholders' equity, consolidated statements of cash flows, or net income (in thousands, except per share data).

	Twelve Months Ended September 30, 2018
	As Previously Reported		As Restated
Net income per common share available to common shareholders - Basic	$	2.46	$	1.34
Shares used in computing net income per common share available to common shareholders - Basic		13,516		24,826
Net income per common share available to common shareholders - Diluted	$	1.32	$	1.32
Shares used in computing net income per common share available to common shareholders - Diluted		25,171		25,257

	Twelve Months Ended September 30, 2017
	As Previously Reported		As Restated
Net income per common share available to common shareholders - Basic	$	3.01	$	1.41
Shares used in computing net income per common share available to common shareholders - Basic		10,919		23,201
Net income per common share available to common shareholders - Diluted	$	1.40	$	1.40
Shares used in computing net income per common share available to common shareholders - Diluted		23,386		23,370

Common Stock

12 Months Ended

Sep. 30, 2019

Stockholders Equity Note [Abstract]

Common Stock

11.	Common Stock

The Company previously issued warrants to third parties, which had a five-year term to be converted to common stock at an exercise price of $0.004 per share. Certain persons who are not U.S. citizens currently hold outstanding warrants to purchase shares of the Company's common stock. The warrants are exercisable if consistent with federal law, which requires that no more than 24.9% of the Company's stock be voted, directly or indirectly, or controlled by persons who are not U.S. citizens. The warrants can be converted to common stock upon warrant holders demonstrating U.S. citizenship or if consistent with above described federal law ownership limitations. In June 2018, the Company and holders agreed to extend the term of outstanding warrants set to expire by five years (through fiscal year 2023).

On June 28, 2018, the Company agreed with GE Capital Aviation Services LLC ("GE Capital") to terminate a warrant to purchase 250,000 shares of common stock held by GE Capital.

In July 2018, the Company's Board of Directors and Compensation Committee approved the issuance of shares of restricted common stock under its 2018 Plan immediately following completion of the Company's IPO to certain of its employees and directors in exchange for the cancellation of existing restricted phantom stock units, unvested restricted shares and SARs. The shares of restricted common stock issued under the 2018 Plan in exchange for the cancellation of restricted phantom stock units, unvested restricted shares and SARs are subject to vesting on the same terms set forth in the prior vesting schedules and are not subject to acceleration in connection with the 2018 Plan issuances.

On August 8, 2018, the Company filed its Second Amended and Restated Articles of Incorporation, which, among other things: (i) effected a 2.5-for-1 stock split of its common stock; and (ii) increased the authorized number of shares of its common and preferred stock to 125,000,000 and 5,000,000, respectively. All references to share and per share amounts in the Company’s consolidated financial statements have been retrospectively revised to reflect the stock split and increase in authorized shares.

On August 14, 2018, the Company completed its IPO, in which it issued and sold 9,630,000 shares of common stock, no par value, at a public offering price of $12.00 per share (the "Firm Shares"). Additionally, in connection with the IPO, the Company granted the underwriters an option to purchase up to an additional 1,444,500 shares of common stock at the same price. On September 11, 2018, the Company closed the sale of 1,344,500 shares ("Option Shares") of its common stock, in connection with the partial exercise of the overallotment option granted to the underwriters in its IPO. Of the 1,344,500 Option Shares sold, 723,985 were purchased directly from the Company and the remaining 620,515 shares were purchased directly from the selling shareholders. The Firm Shares and Option Shares were sold to the public for a price of $12.00 per share. The aggregate gross proceeds to us from the IPO were approximately $124.2 million. We received $111.7 million in net proceeds after deducting $8.7 million of underwriting discounts and commissions and $3.6 million in offering costs.

On April 9, 2019, and pursuant to Section 4.4 of the 2018 Plan, the board of directors approved an increase in the number of shares authorized for issuance under the 2018 Plan by 1,000,000 shares of common stock resulting in a total of 3,500,000 authorized shares.

The Company has not historically paid dividends on shares of its common stock. Additionally, the Company's aircraft lease facility (the "RASPRO" Lease Facility) with RASPRO Trust 2005, a pass-through trust contains restrictions that limit the Company's ability to or prohibit it from paying dividends to holders of its common stock.

Income Taxes

12 Months Ended

Sep. 30, 2019

Income Tax Disclosure [Abstract]

Income Taxes

12.	Income Taxes

The provision (benefit) for income taxes consists of the following:

	Years Ended September 30,
	2019			2018			2017
	(in thousands)
Current
Federal	$	(138	)	$	—		$	—
State		341			465			359
	$	203		$	465		$	359
Deferred
Federal		13,238			(17,308	)		17,713
State		2,265			(583	)		2,802
	$	15,503		$	(17,891	)	$	20,515
Provision (Benefit) for income taxes	$	15,706		$	(17,426	)	$	20,874

Reconciliation between the effective tax rate on income from continuing operations and the statutory tax rate is as follows:

	Years Ended September 30,
	2019			2018			2017
	(in thousands)
Income tax expense at federal statutory rate	$	13,290		$	3,878		$	18,796
Increase (reduction) in income taxes resulting from:
State taxes, net of federal tax benefit		1,785			660			1,397
Nondeductible stock compensation expenses		(21	)		—			—
Permanent items		261			63			92
Change in valuation allowances		(50	)		(646	)		531
US Tax Cuts and Jobs Act Impact		—			(22,015	)		—
162(m) Limitation		119
Impact of changing rates on deferred tax assets		484			(773	)		(353	)
Expired tax attributes		111			1,088			409
Other		(273	)		319			2
Income tax expense (benefit)	$	15,706		$	(17,426	)	$	20,874

The Company's deferred tax assets as of September 30, 2019 and 2018 are as follows:

	Years Ended September 30,
	2019			2018
	(in thousands)
Net operating carry forwards	$	106,645		$	91,981
Deferred credits		1,882			2,443
Other accrued expenses		2,329			1,871
Prepaids and other		2,576			3,530
State alternative minimum tax		1			1
Other reserves and estimated losses		947			836
Operating lease		4,928			6,399
Allowance for doubtful receivables		—			905
Subtotal	$	119,308		$	107,966
Less: valuation allowance		(1,890	)		(1,940	)
Total net deferred tax assets	$	117,418		$	106,026

Intangibles		(2,204	)		(2,613	)
Property and equipment		(170,517	)		(143,210	)
Total deferred tax liabilities	$	(172,721	)	$	(145,823	)
Net deferred tax liability	$	(55,303	)	$	(39,797	)

The Company has federal and state income tax NOL carryforwards of $478.3 million and $228.3 million, which expire in fiscal years 2027-2037 and 2020-2039, respectively.

The Company believes that it is more likely than not that the benefit from certain state NOL carryforwards will not be realized. In recognition of this risk, the Company has provided a valuation allowance of $1.9 million in fiscal year 2019 and $1.9 million in fiscal year 2018 on the deferred tax assets related to these state NOL carryforwards. If or when recognized, the tax benefits related to any reversal of the valuation allowance on deferred tax assets will be recognized as a reduction of income tax expense.

The federal and state NOL carryforwards in the income tax returns filed included unrecognized tax benefits. The deferred tax assets recognized for those NOLs are presented net of these unrecognized tax benefits.

Because of the change of ownership provisions of the Tax Reform Act of 1986, use of a portion of our NOL and tax credit carryforwards may be limited in future periods. Further, a portion of the carryforwards may expire before being applied to reduce future income tax liabilities. The initial public offering in August of 2018 resulted in a change in ownership under Section 382 of the Internal Revenue Code. Based on the valuation of the Company's stock as of the initial public offering date, the Company does not believe any limitation on the utilization of the Company's current net operating losses would be applicable as of September 30, 2019.

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits:

	Years Ended September 30,
	2019		2018			2017
	(in thousands)
Unrecognized tax benefits — October 1	$	4,688	$	7,547		$	7,547
Gross decreases — tax positions in prior period		—		(2,859	)		—
Unrecognized tax benefits — September 30	$	4,688	$	4,688		$	7,547

The Company’s unrecognized tax benefits of $4.7 million, $4.7 million and $7.5 million as of September 30, 2019, 2018 and 2017, respectively, is included the net deferred tax assets. If recognized, the balance of the uncertain tax benefit would affect the effective tax rate.

We recognize interest accrued related to unrecognized tax benefits and penalties as income tax expense. We have not recorded accrued penalties or interest related to the unrecognized tax benefits noted above as the amounts would result in an adjustment to NOL carry forwards.

We are subject to taxation in the United States and various states. As of September 30, 2019, the Company is no longer subject to U.S. federal or state examinations by taxing authorities for fiscal years prior to 1999.

The Tax Cuts and Jobs Act (the "Tax Act") made broad and complex changes to the U.S. tax code that affected the Company's fiscal year ended September 30, 2018, including but not limited to (1) reducing the U.S. federal corporate tax rate, (2) changing rules related to uses and limitations of NOL carryforwards created in tax years beginning after December 31, 2017, (3) eliminating the corporate alternative minimum tax ("AMT") and changing how existing AMT credits can be realized, and (4) altering bonus depreciation rules that will allow for full expensing of qualified property. The Tax Act reduced the federal corporate tax rate to 21% in the Company's fiscal year ended September 30, 2018 for the period beginning after December 31, 2017. For the fiscal year ended September 30, 2019, and onward, the applicable federal corporate tax rate is 21%.

The SEC staff issued SAB 118, which provided guidance on accounting for the tax effects of the Tax Act. SAB 118 provided a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company was required to reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 was complete. To the extent that a company's accounting for certain income tax effects of the Tax Act was incomplete, but it was able to determine a reasonable estimate, it was required to record a provisional estimate in the financial statements. If a company was not able to determine a provisional estimate to be included in the financial statements, it continued to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. The one year measurement period ended during the Company's first quarter ended December 31, 2018. As a result, the Company finalized provisional amounts originally recorded in connection with the Tax Act in the first quarter of the fiscal year ended September 30, 2019.

In connection with the Company's initial analysis of the impact of the Tax Act, it recorded a discrete net tax benefit of $22.4 million in the period ended September 30, 2018. The Company completed its accounting for the income tax effects of the Tax Act.

The Company's accounting for the Tax Act was completed as follows:

Reduction of U.S. federal corporate tax rate: The Act reduced the corporate tax rate to 21%, effective January 1, 2018. In the fourth quarter of the period ended September 30, 2018, the Company completed its analysis to determine the effect of the reduction of the U.S. federal corporate tax rate and recorded an adjustment of $0.9 million from the amount recorded in the first quarter of the 2018 fiscal year. Consequently, the effect for the fiscal year ended September 30, 2018 was a decrease related to the Company's net deferred tax liabilities of $22.0 million, excluding the valuation allowance. The Company also calculated an increase to its valuation allowance of $0.5 million due to the rate change. The Company recorded a corresponding net adjustment to its deferred income tax benefit of $21.5 million for the period ended September 30, 2018 as part of its completion of the accounting for Tax Act.

For tax years beginning after December 31, 2017, the corporate AMT was repealed. AMT credits in excess of regular tax liability are refundable in the years 2018 through 2021. At September 30, 2018, the Company had $2.5 million of AMT credits, all of which is expected to be refunded. The Company has classified a portion of the refund as a current receivable and a portion has been recorded as long-term receivable as of September 30, 2019. In the first quarter of fiscal 2019, the IRS released an announcement regarding Section 53(e) which no longer subjects taxpayers to a sequestration of its AMT credit refund. As a result, the Company reversed a tax expense of approximately $0.1 million related to an estimated sequestration accrual previously recorded during the tax year ended September 30, 2018, resulting in an income tax benefit of $0.1 million for the tax year ended September 30, 2019.

Valuation allowances: The Company determined whether the federal and state valuation allowance assessments were affected by various aspects of the Tax Act. Any corresponding determinations relating to changes in valuation allowances have, likewise, been completed with no changes identified with respect to the provisional amounts recorded.

Share-Based Compensation

12 Months Ended

Sep. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

13.	Share-Based Compensation

Restricted Stock

In July 2018, the Company’s Board of Directors and Compensation Committee approved the issuance of shares of restricted common stock under its 2018 Plan immediately following the IPO to certain of its employees and directors in exchange for the cancellation of existing restricted phantom stock units, unvested restricted shares and SARs. The shares of restricted common stock issued under the 2018 Plan in exchange for the cancellation of restricted phantom stock units, unvested restricted shares and SARs are subject to vesting on the same terms set forth in the prior vesting schedules and are not subject to acceleration in connection with the 2018 Plan issuances. There were 966,022 vested SARs which were cancelled, exchanged for shares of restricted common stock and issued as restricted stock upon completion of the IPO. Immediately following the IPO, 2,249,147 shares were issued to certain of its employees and directors under the 2018 Plan in exchange for the cancellation of 491,915 unvested restricted phantom stock units, 491,198 unvested restricted shares issued under the 2011 and 2017 Plans and 1,266,034 SARs (966,022 vested and 300,012 unvested). The Company has the right to withhold shares to satisfy tax withholding obligations and the withheld shares become available for future grants. The shares are valued at grant date based upon recent share transactions. From inception of the 2011 Plan through IPO, 2,448,905 shares have been granted, 1,978,550 shares have vested and 470,355 shares have been cancelled. From inception of the 2017 Plan, 31,255 shares have been granted, 10,412 have vested and 20,843 shares have been cancelled. In April 2019, the Company’s Board of Directors increased the number of authorized shares of common stock to management under the 2018 Plan from 2,500,000 to 3,500,000. From inception of the 2018 Plan, 2,571,073 shares have been awarded, 1,700,104 shares have vested and 22,995 shares have been cancelled.

The restricted stock activity for our years ended September 30, 2019, 2018 and 2017 is summarized as follows:

				Weighted-
				Average
	Number			Grant Date
2011 and 2017 Plans	of Shares			Fair Value
Restricted shares unvested at September 30, 2016		757,328		$	5.40
Granted		251,615			4.54
Vested		(233,190	)		5.06
Forfeited		—			—
Restricted shares unvested at September 30, 2017		775,753		$	5.22
Granted		—			—
Vested		(284,555	)		5.26
Cancelled		(491,198	)		5.20
Restricted shares unvested at September 30, 2018		—		$	—

				Weighted-
				Average
	Number			Grant Date
2018 Plan	of Shares			Fair Value
Restricted shares unvested at September 30, 2016		—			—
Granted		—			—
Vested		—			—
Forfeited		—			—
Restricted shares unvested at September 30, 2017		—		$	—
Exchanged Restricted Shares		491,198			5.20
Exchanged Phantom Stock		491,915			12.00
Exchanged SARs		1,266,034			12.00
Exchanged SARs vested prior to exchange		(966,022	)		12.00
Vested		(32,500	)		2.00
Cancelled		—			—
Restricted shares unvested at September 30, 2018		1,250,625		$	9.59
Granted		321,926			8.94
Vested		(701,582	)		9.25
Cancelled		(22,995	)		12.00
Restricted shares unvested at September 30, 2019		847,974		$	9.56

The Company has granted restricted stock awards ("RSAs") and restricted stock units ("RSUs") as part of its long-term incentive compensation to employees and non-employee members of the Board of Directors. RSAs and RSUs generally vest over a period of 3 to 5 years for employees and over one year for members of the Board of Directors. The restricted common stock underlying RSAs are deemed issued and outstanding upon grant, and carry the same voting rights of unrestricted outstanding common stock. The restricted common stock underlying RSUs are not deemed issued or outstanding upon grant, and do not carry any voting rights.

Stock Appreciation Rights

In 2014, the Company implemented a share-based payment plan under which certain executives and directors are eligible to receive grants of SARs (the "SARs Plan"). The SARs provide a participant with the right to receive the aggregate appreciation in stock price over the market price of the Company's common stock at the date of grant, payable in cash. The participant may exercise his or her SARs quarterly after the grant is vested but no later than 10 years after the date of grant. The SARs awards vest ratably over a three year period from the date of grant. The Company had authorized 5,000,000 shares under this plan and had granted 4,204,993 since inception of the plan. Since inception of the plan, 3,687,218 of SARs have vested and 2,088,333 of SARs have been exercised. In August 2018, upon IPO, 517,775 unvested SARs and 1,598,885 vested SARs were cancelled in exchange for 300,012 and 966,022 shares of restricted stock under the 2018 Plan, respectively.

The SARs activity for the years ended September 30, 2018 and 2017 is summarized as follows:

				Weighted-
	Number			Average
	of Shares			Fair Value
SARs unvested at September 30, 2016		2,223,333		$	1.19
Granted		384,160			—
Vested		(1,460,812	)		1.96
Forfeited		(6,668	)		—
SARs unvested at September 30, 2017		1,140,013			—
Granted		—			—
Vested		(622,238	)		—
Cancelled		(517,775	)		8.69
Forfeited		—			—
SARs unvested at September 30, 2018		—		$	—

Phantom Stock

On October 17, 2017, the Company implemented a share-based payment plan under which employees, officers, directors and other individuals providing services to the Company are eligible to receive grants of restricted phantom stock units ("Phantom Stock Plan"). The restricted phantom stock units ("restricted stock units" or "RSUs") provide a participant with the right to receive a cash or stock bonus based on the fair market value of a stated number of RSUs that are vested. The shares of Common Stock that may be subject to RSUs granted under the Plan shall not exceed an aggregate of 1,250,000 shares. All of the RSUs are non-vested and forfeitable as of the grant date and vest over a three-year period. Any vested RSU will be settled by the Company upon vesting but no later than March 15 of the calendar year after the date that the RSUs become vested. The Company had authorized 1,250,000 shares under this plan and had granted 536,538 since inception of the plan. Since inception of the plan, 44,623 RSUs have vested or settled. In August 2018, upon completion of our IPO, 491,915 unvested RSUs were cancelled in exchange for shares of restricted stock under the 2018 Plan.

The phantom stock activity for the years ended September 30, 2018 were summarized as follows:

				Weighted-
	Number			Average
	of Shares			Fair Value
Phantom stock unvested at September 30, 2017		—		$	—
Granted		536,538			6.14
Vested		(44,623	)		7.30
Cancelled		(491,915	)		12.00
Phantom stock unvested at September 30, 2018		—		$	—

Following the IPO there will be no further grants under the Stock Appreciation Rights and Phantom Stock plans. Immediately following the IPO, shares of restricted common stock were issued to certain of its employees and directors under its 2018 Plan in exchange for the cancellation of existing restricted phantom stock units, unvested restricted shares and SARs. The shares of restricted common stock issued under the 2018 Plan in exchange for the cancellation of restricted phantom stock units, unvested restricted shares and SARs are subject to vesting on the same terms set forth in the prior vesting schedules and are not subject to acceleration in connection with the 2018 Plan issuances.

As of September 30, 2019, there was $5.9 million, of total unrecognized compensation cost related to unvested share-based compensation arrangements. That cost is expected to be recognized over a weighted-average period of 1.5 years.

Compensation cost for share-based awards are recognized on a straight-line basis over the vesting period. Share-based compensation expense for the years ended September 30, 2019, 2018 and 2017 was $5.5 million, $12.9 million and $2.3 million, respectively. Share-based compensation expenses are recorded in general and administrative expenses in the consolidated statements of operations.

The Company repurchased 205,235 shares of its common stock for $1.9 million to cover the income tax obligation on vested employee equity awards and warrant conversions during the fiscal year ended September 30, 2019. During the fiscal year ended September 30, 2018, the Company repurchased 438,541 shares of its common stock for $5.0 million to cover the income tax obligation on vested employee equity awards.

Commitments

12 Months Ended

Sep. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments

15.	Commitments

At September 30, 2019, the Company leased 18 aircraft under non-cancelable operating leases with remaining terms of up to 4.5 years. The Company has the option to terminate certain leases at various times throughout the lease. The Company headquarters and other facility non-cancelable operating leases have remaining terms of up to 6.2 years. The leases require the Company to pay all taxes, maintenance, insurance, and other operating expenses. Rental expense is recognized on a straight-line basis over the lease term, net of lessor rebates and other incentives. Aggregate rental expense under all operating aircraft, equipment and facility leases totaled approximately $72.8 million, $85.9 million and $83.8 million for the years ended September 30, 2019, 2018 and 2017, respectively.

Future minimum lease payments as of September 30, 2019, under non-cancelable operating leases are as follows (in thousands):

Periods Ending September 30,	Aircraft		Other		Total
2020	$	44,231	$	3,583	$	47,814
2021		44,314		1,693		46,007
2022		29,751		1,339		31,090
2023		12,418		1,308		13,726
2024		11,849		1,336		13,185
Thereafter		—		1,368		1,368
Total	$	142,563	$	10,627	$	153,190

The majority of the Company's leased aircraft are leased through trusts that have a sole purpose to purchase, finance, and lease these aircraft to the Company; therefore, they meet the criteria of a variable interest entity. However, since these are single-owner trusts in which the Company does not participate, the Company is not at risk for losses and is not considered the primary beneficiary. Management believes that the Company's maximum exposure under these leases is the remaining lease payments.

Selected Consolidated Quarterly Financial Data (Unaudited)

12 Months Ended

Sep. 30, 2019

Quarterly Financial Information Disclosure [Abstract]

Selected Consolidated Quarterly Financial Data (Unaudited)

17.	Selected Consolidated Quarterly Financial Data (unaudited)

The following table sets forth certain unaudited selected consolidated financial information for each of the four quarters in the years ended September 30, 2019, 2018 and 2017. In management's opinion, this unaudited consolidated quarterly selected information has been prepared on the same basis as the audited consolidated financial statements and includes all necessary adjustments, consisting only of normal recurring adjustments, which management considers necessary for a fair presentation when read in conjunction with the Consolidated Financial Statements and notes. We believe these comparisons of consolidated quarterly selected financial data are not necessarily indicative of future performance.

Quarterly EPS may not total to the fiscal year EPS due to the weighted average number of shares outstanding at the end of each period reported and rounding.

	12/31/2018		3/31/2019		6/30/2019		9/30/2019
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
	(in thousands, except per share data)
2019
Contract revenue	$	170,449	$	169,771	$	170,366	$	172,248
Total operating revenues		178,156		177,147		180,224		187,830
Operating income		39,230		34,377		17,077		30,453
Net income (loss)		19,081		13,249		3,007		12,243
Net (loss) income per share attributable to common shareholders
Basic		0.55		0.38		0.09		0.35
Diluted		0.54		0.38		0.09		0.35

	12/31/2017		3/31/2018		6/30/2018			9/30/2018
	First		Second		Third			Fourth
	Quarter		Quarter		Quarter			Quarter
	(in thousands, except per share data)
2018
Contract revenue	$	154,389	$	156,515	$	159,916		$	168,444
Total operating revenues		164,684		167,640		171,739			177,532
Operating income		15,023		16,349		(508	)		41,784
Net income (loss)		22,624		2,372		(11,135	)		19,394
Net (loss) income per share attributable to common shareholders
Basic		0.97		0.10		(0.48	)		0.66
Diluted		0.96		0.10		(0.48	)		0.65

	12/31/2016		3/31/2017		6/30/2017		9/30/2017
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
	(in thousands, except per share data)
2017
Contract revenue	$	155,502	$	154,210	$	157,411	$	151,575
Total operating revenues		160,235		159,096		166,952		157,293
Operating income		20,838		20,405		36,360		22,691
Net income		6,610		5,304		15,432		5,482
Net (loss) income per share attributable to common shareholders
Basic		0.28		0.23		0.67		0.24
Diluted		0.28		0.23		0.66		0.24

Restatement

Subsequent to the issuance of the Company’s condensed consolidated financial statements for the three months ended December 31, 2018, we determined our previously issued condensed consolidated financial statements included warrants with a nominal conversion price in diluted income per common share available to common shareholders, however, they should have been included in basic income per common share available to common shareholders. Since diluted shares are under the treasury stock method, diluted income per common share available to common shareholders was impacted by this change. As a result, basic and diluted income per common share available to common shareholders for the quarters ended March 31, June 30, September 30 and December 31, 2018 and 2017 and the quarter ended December 31, 2016 have been restated to appropriately include the warrants with a nominal conversion price in basic income per common share available to common shareholders.

	Three Months Ended December 31, 2018
	As Previously Reported		As Restated
Net income per share attributable to common shareholders
Basic	$	0.80	$	0.55
Diluted	$	0.55	$	0.54

	Three Months Ended December 31, 2017				Three Months Ended March 31, 2018				Three Months Ended June 30, 2018						Three Months Ended September 30, 2018
	As Previously Reported		As Restated		As Previously Reported		As Restated		As Previously Reported			As Restated			As Previously Reported		As Restated
Net income (loss) per share attributable to common shareholders
Basic	$	2.00	$	0.97	$	0.20	$	0.10	$	(0.89	)	$	(0.48	)	$	1.04	$	0.66
Diluted	$	0.96	$	0.96	$	0.10	$	0.10	$	(0.89	)	$	(0.48	)	$	0.65	$	0.65

	Three Months Ended December 31, 2016				Three Months Ended March 31, 2017				Three Months Ended June 30, 2017						Three Months Ended September 30, 2017
	As Previously Reported		As Restated		As Previously Reported		As Restated		As Previously Reported			As Restated			As Previously Reported		As Restated
Net income per share attributable to common shareholders
Basic	$	0.62	$	0.28	$	0.48	$	0.23	$	1.40		$	0.67		$	0.49	$	0.24
Diluted	$	0.28	$	0.28	$	0.23	$	0.23	$	0.66		$	0.66		$	0.23	$	0.24

Subsequent Events

12 Months Ended

Sep. 30, 2019

Subsequent Events [Abstract]

Subsequent Events

18.	Subsequent Events

On November 26, 2019, the Company entered into an Amended and Restated Capacity Purchase Agreement with United, which amends and restates the United Capacity Purchase Agreement, dated as of August 29, 2013 (the "Original United CPA"). The Company entered into the Amended and Restated Capacity Purchase Agreement to, among other things, incorporate the terms of the 11 prior amendments to that Agreement, as well as agree upon the terms described below.

The term of the Amended and Restated Capacity Purchase Agreement was extended through the addition of 20 new Embraer E175LL aircraft to the scope of such agreement, which aircraft will be financed and owned by the Company and operated for a period of 12 years from the in-service date. The addition of these new aircraft increases the Company’s Embraer fleet to 80 aircraft. Deliveries are scheduled to begin in May 2020 and be completed by December 31, 2020. Commencing five (5) years after the actual in-service date, United has the right to remove the new E175LL aircraft from service by giving the Company 90 days or more notice, subject to certain conditions, including the payment of certain wind-down expenses plus, if removed prior to the ten (10) year anniversary of the in-service date, certain accelerated margin payments. In addition to adding the 20 new E175LL aircraft, the Company also extended the term of the 42 E175 aircraft leased from United for an additional five (5) years.

In connection with the new Embraer E175LL aircraft deliveries, the Company has agreed to lease its twenty (20) CRJ700 aircraft to another United Express service provider for a term of seven years. The form of lease or sublease is to be mutually agreed upon between the parties, subject to receipt of any required third party consents. The lessee must pay the Company a specified total per month for each aircraft plus specified supplemental rent payments for maintenance. The other United Express carrier will be responsible for all obligations under the leases. However, subject to certain limits and requirements. United will be responsible for certain unmet rent obligations under the leases. In addition, United has a right to purchase the twenty (20) CRJ700 aircraft from Mesa at fair market value before or during the lease term.

On November 25, 2019, the Company amended its agreement with American Airlines. The Company did not meet certain performance metrics during the most recent measurement period, which allows American to remove two additional aircraft from the capacity purchase agreement. American has agreed to defer the right to remove these two aircraft but has elected to remove one of two previously deferred aircraft, effective January 2, 2020.

One December 11, 2019, the Company entered into a purchase agreement with General Electric Company to purchase twenty (20) new spare CF34-8C5 engines. The Company expects to take delivery of the engines between August 2020 and December 2021.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Segment Reporting

Cash and Cash Equivalents

The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.

Marketable Securities

Restricted Cash

Expendable Parts and Supplies

Prepaid Expenses

Property and Equipment

Estimated useful lives of the various classifications of property and equipment are as follows:

Property and Equipment		Estimated Useful Life
Buildings		30 years
Aircraft		25 years from manufacture date
Flight equipment		7-20 years
Equipment		5-9 years
Furniture and fixtures		3-5 years
Vehicles		5 years
Rotable spare parts		Life of the aircraft or term of the lease, whichever is less
Leasehold improvements		Life of the aircraft or term of the lease, whichever is less

Fair Value Measurements

▪

Level 1 – Observable inputs such as quoted prices in active markets;

▪

Level 2 – Inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and

▪

Level 3 – Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

Prepaid Maintenance Deposits

Debt Financing Costs

Unutilized Manufacturer Credits

Intangibles

Other Assets

Other long-term assets primarily consist of noncurrent deferred reimbursed costs, debt financing costs, and prepaid maintenance deposits.

Income Taxes

Other Noncurrent Liabilities

Adoption of New Revenue Standard

Revenue Recognition, Contract Liabilities and Contract Assets

Revenue Recognition

Contract Liabilities

Contract Assets

Maintenance Expense

Aircraft Leases

Changes in Accounting Policy

Change in Accounting Policy

Balance Sheet Information (Tables)

12 Months Ended

Sep. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Summary of Certain Significant Amounts Included in Condensed Consolidated Balance Sheet

Certain significant amounts included in the Company's consolidated balance sheet as of September 30, 2019 and 2018, consisted of the following (in thousands):

	September 30,			September 30,
	2019			2018
Expendable parts and supplies, net
Expendable parts and supplies	$	25,336		$	18,907
Less obsolescence and other		(3,999	)		(3,249	)
	$	21,337		$	15,658
Prepaid expenses and other current assets
Prepaid aircraft rent	$	35,786		$	30,267
Unutilized manufacturer credits		—			4,500
Deferred offering and reimbursed costs		2,092			1,945
Other		3,045			4,202
	$	40,923		$	40,914
Property and equipment—net
Aircraft and other flight equipment substantially pledged	$	1,582,199		$	1,502,940
Other equipment		5,122			3,721
Leasehold improvements		2,797			2,754
Vehicles		924			692
Building		699			699
Furniture and fixtures		302			287
Total property and equipment		1,592,043			1,511,093
Less accumulated depreciation		(318,458	)		(260,264	)
	$	1,273,585		$	1,250,829
Other accrued expenses
Accrued property taxes	$	9,186		$	6,981
Accrued interest		4,497			6,118
Accrued vacation		6,128			5,470
Accrued wheels, brakes and tires		1,513			1,452
Other		7,564			9,675
	$	28,888		$	29,696

Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Carrying Value and Estimated Fair Value of Long-term Debt, Including Current Maturities

The carrying value and estimated fair value of the Company's long-term debt, including current maturities, were as follows (in millions):

	September 30, 2019				September 30, 2018
	Carrying		Fair		Carrying		Fair
	Value		Value		Value		Value
Long-term debt, including current maturities⁽¹⁾	$	858.1	$	882.7	$	930.2	$	926.2

⁽¹⁾	Current and prior period long-term debts' carrying and fair values exclude net debt issuance costs.

Long-Term Debt and Other Borrowings (Tables)

12 Months Ended

Sep. 30, 2019

Debt Disclosure [Abstract]

Schedule of Long-term Debt

Long-term debt as of September 30, 2019 and 2018, consisted of the following (in thousands):

	September 30,			September 30,
	2019			2018
Notes payable to financial institution, collateralized by the underlying aircraft, due 2019⁽¹⁾⁽²⁾	$	—		$	4,428
Notes payable to financial institution, collateralized by the underlying aircraft, due 2022⁽³⁾⁽⁴⁾		49,795			69,340
Notes payable to financial institution, collateralized by the underlying aircraft, due 2024⁽⁵⁾		60,761			72,438
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2027⁽⁶⁾		110,912			122,591
Notes payable to secured parties, collateralized by the underlying aircraft, due 2028⁽⁷⁾		191,168			209,240
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2028⁽⁸⁾		152,945			167,269
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2022⁽¹⁶⁾		71,998			95,060
Notes payable to financial institution, collateralized by the underlying equipment, due 2022⁽⁹⁾		—			88,162
Senior and subordinated notes payable to secured parties, collateralized by the underlying aircraft, due 2022⁽¹⁰⁾		47,309			63,403
Notes payable to financial institution, collateralized by the underlying equipment, due 2020⁽¹¹⁾		1,659			3,318
Notes payable to financial institution due 2020⁽¹²⁾		2,329			4,360
Notes payable to financial institution, collateralized by the underlying equipment, due 2020⁽¹³⁾		6,962			14,971
Notes payable to financial institution due 2019⁽¹⁴⁾		—			5,896
Other obligations due to financial institution, collateralized by the underlying equipment, due 2023⁽¹⁵⁾		8,530			9,731
Notes payable to financial institution, collateralized by the underlying equipment, due 2024⁽¹⁷⁾		80,153			—
Notes payable to financial institution, collateralized by the underlying aircraft, due 2023⁽¹⁸⁾		65,625			—
Notes payable to financial institution due 2023 ⁽¹⁹⁾		8,000			—
Total long-term debt		858,145			930,207
Less current portion		(165,900	)		(155,170	)
Less unamortized debt issuance costs		(14,822	)		(14,860	)

Long-term debt—excluding current portion	$	677,423		$	760,177

⁽¹⁾	In fiscal 2005, the Company financed five CRJ-900 aircraft with $118 million in debt. The debt bears interest at the monthly London InterBank Offered Rate ("LIBOR"), plus 3% and requires monthly principal and interest payments. As of September 30, 2019, the loan has been repaid.

⁽²⁾	In fiscal 2004, the Company financed five CRJ-700 and nine CRJ 900 aircraft with $254.7 million in debt. The debt bears interest at the monthly LIBOR plus 3% and requires monthly principal and interest payments. As of September 30, 2019, the loan has been repaid.

⁽³⁾	In fiscal 2007, the Company financed three CRJ-900 and three CRJ-700 aircraft for $120.3 million. The debt bears interest at the monthly LIBOR plus 2.25% (4.270% at September 30, 2019) and requires monthly principal and interest payments.

⁽⁴⁾	In fiscal 2014, the Company financed 10 CRJ-900 aircraft for $88.4 million. The debt bears interest at the monthly LIBOR plus a spread ranging from 1.95% to 7.25% (3.970% to 9.270% at September 30, 2019) and requires monthly principal and interest payments.

⁽⁵⁾	In fiscal 2014, the Company financed eight CRJ-900 aircraft with $114.5 million in debt. The debt bears interest at 5% and requires monthly principal and interest payments.

⁽⁶⁾

⁽⁷⁾	In fiscal 2017, the Company financed 10 E-175 aircraft with $246 million in debt under an EETC financing arrangement (see discussion below). The debt bears interest ranging from 4.75% to 6.25% and requires semi-annual principal and interest payments.

⁽⁸⁾

⁽⁹⁾	In fiscal 2018, the Company financed certain flight equipment with $99.1 million in debt. The debt bears interest at the monthly LIBOR (rounded to the nearest 16th) plus 7.25% and requires monthly principal and interest payments. As of September 30, 2019, the loan has been repaid.

⁽¹⁰⁾

⁽¹¹⁾	In fiscal 2015, the Company financed certain flight equipment with $8.3 million in debt. The debt bears interest at 5.163% and requires monthly principal and interest payments.

⁽¹²⁾	In fiscal 2015 and 2017, the Company financed certain flight equipment maintenance costs with $10.2 million in debt. The debt bears interest at the three-month LIBOR plus 3.07% (5.160% at September 30, 2019) and requires quarterly principal and interest payments.

⁽¹³⁾

⁽¹⁴⁾

⁽¹⁵⁾	In February 2018, the Company leased two spare engines. The leases were determined to be capital as the leases contain a bargain purchase option at the end of the term. Imputed interest is 9.128% and the leases requires monthly payments.

⁽¹⁶⁾

⁽¹⁷⁾	In January 2019, the Company financed certain flight equipment with $91.2 million in debt. The debt bears interest at the monthly LIBOR plus 3.10% (5.120% at September 30, 2019) and requires monthly principal and interest payments.

⁽¹⁸⁾	In June 2019, the Company financed ten CRJ-700 aircraft with $70.0 million in debt, which were previously leased. The debt bears interest at the monthly LIBOR plus 5.25% (7.270% at September 30, 2019) and requires monthly principal and interest payments.

⁽¹⁹⁾

Schedule of Principal Maturities of Long-term Debt

Principal maturities of long-term debt as of September 30, 2019, and for each of the next five years are as follows (in thousands):

	Total Principal
Periods Ending September 30,	Amount
2020		165,900
2021		161,359
2022		152,745
2023		103,165
2024		71,033
Thereafter		203,943
	$	858,145

Earnings Per Share (Tables)

12 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Calculations of Net Income Per Common Share

Calculations of net income per common share were as follows (in thousands, except per share data):

	Year Ended September 30,
	2019		2018		2017
Net income	$	47,580	$	33,255	$	32,828
Basic weighted average common shares outstanding		34,764		24,826		23,201
Add: Incremental shares for:
Dilutive effect of warrants		—		116		93
Dilutive effect of restricted stock		300		315		76
Diluted weighted average common shares outstanding		35,064		25,257		23,370

Net income per common share
Basic	$	1.37	$	1.34	$	1.41
Diluted	$	1.36	$	1.32	$	1.40

Restatement (Tables)

12 Months Ended

Sep. 30, 2019

Accounting Changes And Error Corrections [Abstract]

Summary of Basic and Diluted Net Income per Common Share Available to Common Shareholders

	Twelve Months Ended September 30, 2018
	As Previously Reported		As Restated
Net income per common share available to common shareholders - Basic	$	2.46	$	1.34
Shares used in computing net income per common share available to common shareholders - Basic		13,516		24,826
Net income per common share available to common shareholders - Diluted	$	1.32	$	1.32
Shares used in computing net income per common share available to common shareholders - Diluted		25,171		25,257

	Twelve Months Ended September 30, 2017
	As Previously Reported		As Restated
Net income per common share available to common shareholders - Basic	$	3.01	$	1.41
Shares used in computing net income per common share available to common shareholders - Basic		10,919		23,201
Net income per common share available to common shareholders - Diluted	$	1.40	$	1.40
Shares used in computing net income per common share available to common shareholders - Diluted		23,386		23,370

	Three Months Ended December 31, 2018
	As Previously Reported		As Restated
Net income per share attributable to common shareholders
Basic	$	0.80	$	0.55
Diluted	$	0.55	$	0.54

	Three Months Ended December 31, 2017				Three Months Ended March 31, 2018				Three Months Ended June 30, 2018						Three Months Ended September 30, 2018
	As Previously Reported		As Restated		As Previously Reported		As Restated		As Previously Reported			As Restated			As Previously Reported		As Restated
Net income (loss) per share attributable to common shareholders
Basic	$	2.00	$	0.97	$	0.20	$	0.10	$	(0.89	)	$	(0.48	)	$	1.04	$	0.66
Diluted	$	0.96	$	0.96	$	0.10	$	0.10	$	(0.89	)	$	(0.48	)	$	0.65	$	0.65

	Three Months Ended December 31, 2016				Three Months Ended March 31, 2017				Three Months Ended June 30, 2017						Three Months Ended September 30, 2017
	As Previously Reported		As Restated		As Previously Reported		As Restated		As Previously Reported			As Restated			As Previously Reported		As Restated
Net income per share attributable to common shareholders
Basic	$	0.62	$	0.28	$	0.48	$	0.23	$	1.40		$	0.67		$	0.49	$	0.24
Diluted	$	0.28	$	0.28	$	0.23	$	0.23	$	0.66		$	0.66		$	0.23	$	0.24

Income Taxes (Tables)

12 Months Ended

Sep. 30, 2019

Income Tax Disclosure [Abstract]

Schedule of Provision (Benefit) for Income Taxes

The provision (benefit) for income taxes consists of the following:

	Years Ended September 30,
	2019			2018			2017
	(in thousands)
Current
Federal	$	(138	)	$	—		$	—
State		341			465			359
	$	203		$	465		$	359
Deferred
Federal		13,238			(17,308	)		17,713
State		2,265			(583	)		2,802
	$	15,503		$	(17,891	)	$	20,515
Provision (Benefit) for income taxes	$	15,706		$	(17,426	)	$	20,874

Schedule of Reconciliation between Effective Tax Rate Income from Continuing Operations and Statutory Rate

Reconciliation between the effective tax rate on income from continuing operations and the statutory tax rate is as follows:

	Years Ended September 30,
	2019			2018			2017
	(in thousands)
Income tax expense at federal statutory rate	$	13,290		$	3,878		$	18,796
Increase (reduction) in income taxes resulting from:
State taxes, net of federal tax benefit		1,785			660			1,397
Nondeductible stock compensation expenses		(21	)		—			—
Permanent items		261			63			92
Change in valuation allowances		(50	)		(646	)		531
US Tax Cuts and Jobs Act Impact		—			(22,015	)		—
162(m) Limitation		119
Impact of changing rates on deferred tax assets		484			(773	)		(353	)
Expired tax attributes		111			1,088			409
Other		(273	)		319			2
Income tax expense (benefit)	$	15,706		$	(17,426	)	$	20,874

Schedule of Deferred Tax Assets

The Company's deferred tax assets as of September 30, 2019 and 2018 are as follows:

	Years Ended September 30,
	2019			2018
	(in thousands)
Net operating carry forwards	$	106,645		$	91,981
Deferred credits		1,882			2,443
Other accrued expenses		2,329			1,871
Prepaids and other		2,576			3,530
State alternative minimum tax		1			1
Other reserves and estimated losses		947			836
Operating lease		4,928			6,399
Allowance for doubtful receivables		—			905
Subtotal	$	119,308		$	107,966
Less: valuation allowance		(1,890	)		(1,940	)
Total net deferred tax assets	$	117,418		$	106,026

Intangibles		(2,204	)		(2,613	)
Property and equipment		(170,517	)		(143,210	)
Total deferred tax liabilities	$	(172,721	)	$	(145,823	)
Net deferred tax liability	$	(55,303	)	$	(39,797	)

Schedule of Reconciliation of Total Amounts of Unrecognized Tax Benefits

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits:

	Years Ended September 30,
	2019		2018			2017
	(in thousands)
Unrecognized tax benefits — October 1	$	4,688	$	7,547		$	7,547
Gross decreases — tax positions in prior period		—		(2,859	)		—
Unrecognized tax benefits — September 30	$	4,688	$	4,688		$	7,547

Share-Based Compensation (Tables)

12 Months Ended

Sep. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Restricted Stock Activity

The restricted stock activity for our years ended September 30, 2019, 2018 and 2017 is summarized as follows:

				Weighted-
				Average
	Number			Grant Date
2011 and 2017 Plans	of Shares			Fair Value
Restricted shares unvested at September 30, 2016		757,328		$	5.40
Granted		251,615			4.54
Vested		(233,190	)		5.06
Forfeited		—			—
Restricted shares unvested at September 30, 2017		775,753		$	5.22
Granted		—			—
Vested		(284,555	)		5.26
Cancelled		(491,198	)		5.20
Restricted shares unvested at September 30, 2018		—		$	—

				Weighted-
				Average
	Number			Grant Date
2018 Plan	of Shares			Fair Value
Restricted shares unvested at September 30, 2016		—			—
Granted		—			—
Vested		—			—
Forfeited		—			—
Restricted shares unvested at September 30, 2017		—		$	—
Exchanged Restricted Shares		491,198			5.20
Exchanged Phantom Stock		491,915			12.00
Exchanged SARs		1,266,034			12.00
Exchanged SARs vested prior to exchange		(966,022	)		12.00
Vested		(32,500	)		2.00
Cancelled		—			—
Restricted shares unvested at September 30, 2018		1,250,625		$	9.59
Granted		321,926			8.94
Vested		(701,582	)		9.25
Cancelled		(22,995	)		12.00
Restricted shares unvested at September 30, 2019		847,974		$	9.56

Schedule of SARs Activity

The SARs activity for the years ended September 30, 2018 and 2017 is summarized as follows:

				Weighted-
	Number			Average
	of Shares			Fair Value
SARs unvested at September 30, 2016		2,223,333		$	1.19
Granted		384,160			—
Vested		(1,460,812	)		1.96
Forfeited		(6,668	)		—
SARs unvested at September 30, 2017		1,140,013			—
Granted		—			—
Vested		(622,238	)		—
Cancelled		(517,775	)		8.69
Forfeited		—			—
SARs unvested at September 30, 2018		—		$	—

Schedule of Phantom Stock Activity

The phantom stock activity for the years ended September 30, 2018 were summarized as follows:

				Weighted-
	Number			Average
	of Shares			Fair Value
Phantom stock unvested at September 30, 2017		—		$	—
Granted		536,538			6.14
Vested		(44,623	)		7.30
Cancelled		(491,915	)		12.00
Phantom stock unvested at September 30, 2018		—		$	—

Commitments (Tables)

12 Months Ended

Sep. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments

Future minimum lease payments as of September 30, 2019, under non-cancelable operating leases are as follows (in thousands):

Periods Ending September 30,	Aircraft		Other		Total
2020	$	44,231	$	3,583	$	47,814
2021		44,314		1,693		46,007
2022		29,751		1,339		31,090
2023		12,418		1,308		13,726
2024		11,849		1,336		13,185
Thereafter		—		1,368		1,368
Total	$	142,563	$	10,627	$	153,190

Selected Consolidated Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Sep. 30, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Selected Consolidated Financial Information

Quarterly EPS may not total to the fiscal year EPS due to the weighted average number of shares outstanding at the end of each period reported and rounding.

	12/31/2018		3/31/2019		6/30/2019		9/30/2019
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
	(in thousands, except per share data)
2019
Contract revenue	$	170,449	$	169,771	$	170,366	$	172,248
Total operating revenues		178,156		177,147		180,224		187,830
Operating income		39,230		34,377		17,077		30,453
Net income (loss)		19,081		13,249		3,007		12,243
Net (loss) income per share attributable to common shareholders
Basic		0.55		0.38		0.09		0.35
Diluted		0.54		0.38		0.09		0.35

	12/31/2017		3/31/2018		6/30/2018			9/30/2018
	First		Second		Third			Fourth
	Quarter		Quarter		Quarter			Quarter
	(in thousands, except per share data)
2018
Contract revenue	$	154,389	$	156,515	$	159,916		$	168,444
Total operating revenues		164,684		167,640		171,739			177,532
Operating income		15,023		16,349		(508	)		41,784
Net income (loss)		22,624		2,372		(11,135	)		19,394
Net (loss) income per share attributable to common shareholders
Basic		0.97		0.10		(0.48	)		0.66
Diluted		0.96		0.10		(0.48	)		0.65

	12/31/2016		3/31/2017		6/30/2017		9/30/2017
	First		Second		Third		Fourth
	Quarter		Quarter		Quarter		Quarter
	(in thousands, except per share data)
2017
Contract revenue	$	155,502	$	154,210	$	157,411	$	151,575
Total operating revenues		160,235		159,096		166,952		157,293
Operating income		20,838		20,405		36,360		22,691
Net income		6,610		5,304		15,432		5,482
Net (loss) income per share attributable to common shareholders
Basic		0.28		0.23		0.67		0.24
Diluted		0.28		0.23		0.66		0.24

Summary of Basic and Diluted Net Income per Common Share Available to Common Shareholders

	Twelve Months Ended September 30, 2018
	As Previously Reported		As Restated
Net income per common share available to common shareholders - Basic	$	2.46	$	1.34
Shares used in computing net income per common share available to common shareholders - Basic		13,516		24,826
Net income per common share available to common shareholders - Diluted	$	1.32	$	1.32
Shares used in computing net income per common share available to common shareholders - Diluted		25,171		25,257

	Twelve Months Ended September 30, 2017
	As Previously Reported		As Restated
Net income per common share available to common shareholders - Basic	$	3.01	$	1.41
Shares used in computing net income per common share available to common shareholders - Basic		10,919		23,201
Net income per common share available to common shareholders - Diluted	$	1.40	$	1.40
Shares used in computing net income per common share available to common shareholders - Diluted		23,386		23,370

	Three Months Ended December 31, 2018
	As Previously Reported		As Restated
Net income per share attributable to common shareholders
Basic	$	0.80	$	0.55
Diluted	$	0.55	$	0.54

	Three Months Ended December 31, 2017				Three Months Ended March 31, 2018				Three Months Ended June 30, 2018						Three Months Ended September 30, 2018
	As Previously Reported		As Restated		As Previously Reported		As Restated		As Previously Reported			As Restated			As Previously Reported		As Restated
Net income (loss) per share attributable to common shareholders
Basic	$	2.00	$	0.97	$	0.20	$	0.10	$	(0.89	)	$	(0.48	)	$	1.04	$	0.66
Diluted	$	0.96	$	0.96	$	0.10	$	0.10	$	(0.89	)	$	(0.48	)	$	0.65	$	0.65

	Three Months Ended December 31, 2016				Three Months Ended March 31, 2017				Three Months Ended June 30, 2017						Three Months Ended September 30, 2017
	As Previously Reported		As Restated		As Previously Reported		As Restated		As Previously Reported			As Restated			As Previously Reported		As Restated
Net income per share attributable to common shareholders
Basic	$	0.62	$	0.28	$	0.48	$	0.23	$	1.40		$	0.67		$	0.49	$	0.24
Diluted	$	0.28	$	0.28	$	0.23	$	0.23	$	0.66		$	0.66		$	0.23	$	0.24

Organization and Operations - Additional Information (Detail)						1 Months Ended				12 Months Ended
	Nov. 26, 2019 Air-craft	Sep. 30, 2019 Daily_Departure State Air-craft shares	Sep. 11, 2018 USD ($) $ / shares shares	Aug. 14, 2018 USD ($) $ / shares shares	Aug. 08, 2018 shares	Aug. 28, 2019 Air-craft	Jul. 31, 2019 Air-craft	Apr. 30, 2019 shares	Jul. 31, 2018 shares	Sep. 30, 2019 USD ($) Daily_Departure State Air-craft City shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 shares	Apr. 02, 2019 Air-craft
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of states in which entity operates \| State		39								39
Number of aircrafts operated \| Air-craft										145
Number of cities in which entity operates \| City										125
Number of daily departures \| Daily_Departure		730								730
Common stock, stock split										Effected a 2.5-for-1 stock split
Stock split ratio					2.5
Common stock, shares authorized		125,000,000			125,000,000					125,000,000	125,000,000
Preferred stock, shares authorized		5,000,000			5,000,000					5,000,000	5,000,000
Stock issued during period, shares, new issues			1,344,500
Common stock, warrants issued		3,600,953								3,600,953	10,614,990
Gross proceeds from sale of shares \| $			$ 124,247,820								$ 124,246,000
Maximum number of aircraft to permanently withdraw in the event company fails to meet new/ revise performance metrics \| Air-craft		6
Number of aircraft converted to be utilized as operational spares \| Air-craft													2
Number of aircraft permanently withdraw due to failure to meet new/revised performance metrics \| Air-craft							2
Number of additional aircraft permanently withdrawn due to company's failure to meet certain performance metrics \| Air-craft						2
Payment of lease cost \| $											$ 1,900,000
Number of leased aircraft \| Air-craft		18								18
Notice period for termination of agreement										The capacity purchase agreement is also subject to early termination for cause under specified circumstances and subject to the Company's right to cure under certain circumstances. United is also permitted, subject to certain conditions, to terminate the agreement early in its discretion by giving us notice of 90 days or more.
CRJ-900 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft										62
CRJ-700 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft										20
E-175 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft										60
E-175 Aircraft [Member] \| Mesa [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft										18
E-175 Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts purchased \| Air-craft										42
American Airlines Inc. [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ownership interest		7.10%								7.10%	7.20%
2018 Equity Incentive Plan [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock withheld to cover tax withholding requirements upon vesting to restricted stock units shares				314,198
Restricted stock, shares issued net of shares for tax withholdings				651,824
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues									2,249,147
Number of Shares, Granted				1,266,034				2,571,073		321,926		0
Number of Shares, vested				966,022
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member] \| Employees [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional restricted common stock shares issued				983,113
2011 and 2017 Plans [Member] \| Restricted Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of Shares, Granted											0	251,615
2011 and 2017 Plans [Member] \| Restricted Stock [Member] \| Employees [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Cancellation of common stock shares existing unvested restricted phantom units				491,915
Cancellation of common stock shares existing of unvested restricted stock				491,198
IPO [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues				9,630,000
Shares issued, price per share \| $ / shares				$ 12.00
Gross proceeds of initial public offering \| $				$ 115,600,000						$ 124,200,000
Underwriter Options [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock, warrants issued				1,444,500
Purchased Directly From Company [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues			723,985
Purchased Directly From Selling Shareholders [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, new issues			620,515
Firm Shares and Option Shares [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Shares issued, price per share \| $ / shares			$ 12.00
Subsequent Event [Member] \| CRJ-700 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of leased aircraft \| Air-craft	20
Aircraft lease term	7 years
Subsequent Event [Member] \| CRJ-700 Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aircraft lease term	7 years
Subsequent Event [Member] \| E-175 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of additional aircrafts \| Air-craft	18
Lease expiration year	2028
Subsequent Event [Member] \| E-175 Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft	42
Aircraft lease extension period	5 years
Subsequent Event [Member] \| E-175 Aircraft [Member] \| United [Member] \| Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Lease expiration year	2024
Subsequent Event [Member] \| E-175 Aircraft [Member] \| United [Member] \| Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Lease expiration year	2028
Subsequent Event [Member] \| E175LL Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated \| Air-craft	80
Number of additional aircrafts \| Air-craft	20
Number of years in operation	12 years

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2019 USD ($) Segment	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments \| Segment	1
Number of reportable segments \| Segment	1
Marketable securities	$ 0	$ 19,921,000
Outstanding letters of credit to be collateralized by amounts on deposit, classified as restricted cash	3,600,000	3,800,000
Allowance for obsolete expendable parts and supplies	642,000	200,000	$ 419,000
Reduction of unfavorable lease liability	5,700,000	6,600,000	6,800,000
Write off of unfavorable lease liability	750,000	1,200,000
Lease revenue	219,000,000	217,000,000	217,600,000
Current and non-current deferred credit balances	12,100,000	15,400,000	17,200,000
Recognized deferred credits to revenue	5,100,000	4,400,000	3,800,000
Contract assets balances	3,900,000	4,600,000	6,100,000
Contract cost amortization	2,400,000	1,900,000	1,600,000
Engine overhaul expense	30,000,000	51,200,000	64,000,000
Engine overhaul pass-through expense	6,000,000	12,300,000	300,000
Airframe check expense	17,200,000	21,500,000	22,600,000
Airframe check pass-through expense	400,000	7,500,000	$ 4,900,000
Change in accounting policy , effect of increase in SARs and Phantom Stock liability	2,400,000
Property and Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment charges	0	0
Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Allowance for obsolete expendable parts and supplies	$ 2,400,000	$ 1,800,000
Percentage leased	12.00%
Aircraft and Rotable Spare Parts [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, salvage value, percentage	20.00%
Letter of Credit [Member]
Summary Of Significant Accounting Policies [Line Items]
Letter of credit facility, amount	$ 6,000,000

Summary of Significant Accounting Policies - Summary of Estimated Useful Lives of Various Classifications of Property and Equipment (Detail)	12 Months Ended
	Sep. 30, 2019
Buildings [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	30 years
Aircraft [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	25 years from manufacture date
Flight Equipment [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	7 years
Flight Equipment [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	20 years
Equipment [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	5 years
Equipment [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	9 years
Furniture and Fixtures [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	3 years
Furniture and Fixtures [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	5 years
Vehicles [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	5 years
Rotable Spare Parts [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	Life of the aircraft or term of the lease, whichever is less
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	Life of the aircraft or term of the lease, whichever is less

Recent Accounting Pronouncements - Additional Information (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2019 USD ($) Air-craft	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of leased aircraft \| Air-craft		18
Deferred income taxes		$ 15,503	$ (17,891)	$ 20,515
Income tax expense (benefit)		$ 15,706	$ (17,426)	$ 20,874
Accounting Standards Update 2016-02
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of leased aircraft \| Air-craft		18
Number of nominal operating leased aircraft \| Air-craft		42
Accounting Standards Update 2016-02 \| Minimum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Operating lease, liability		$ 130,000
Operating lease, right-of-use asset		120,000
Accounting Standards Update 2016-02 \| Maximum [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Operating lease, liability		170,000
Operating lease, right-of-use asset		$ 180,000
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Deferred income taxes	$ 400
Income tax expense (benefit)	300
Cumulative-effect adjustment increasing retained earnings	$ 700

Concentrations - Additional Information (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2019 USD ($) Air-craft	Sep. 30, 2018 USD ($)	Sep. 30, 2017
Concentration Risk [Line Items]
Number of aircraft \| Air-craft	17
Allowance for doubtful accounts \| $	$ 1.0	$ 1.3
American Airlines Inc. [Member] \| Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	53.00%	54.00%	56.00%
United [Member] \| Sales Revenue, Net [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	47.00%	46.00%	44.00%

Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Intangible Assets Net Excluding Goodwill [Abstract]
Amortization expense recognized	$ 1.8	$ 0.4	$ 0.4
Amortization expense for 2020	1.5
Amortization expense for 2021	1.2
Amortization expense for 2022	1.0
Amortization expense for 2023	0.9
Amortization expense for 2024	$ 0.8

Balance Sheet Information - Summary of Certain Significant Amounts Included in Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Expendable parts and supplies, net
Expendable parts and supplies	$ 25,336	$ 18,907
Less obsolescence and other	(3,999)	(3,249)
Expendable parts and supplies, net	21,337	15,658
Prepaid expenses and other current assets
Prepaid aircraft rent	35,786	30,267
Unutilized manufacturer credits		4,500
Deferred offering and reimbursed costs	2,092	1,945
Other	3,045	4,202
Prepaid expenses and other current assets	40,923	40,914
Property and equipment-net
Property and equipment-gross	1,592,043	1,511,093
Less accumulated depreciation	(318,458)	(260,264)
Property and equipment-net	1,273,585	1,250,829
Other accrued expenses
Accrued property taxes	9,186	6,981
Accrued interest	4,497	6,118
Accrued vacation	6,128	5,470
Accrued wheels, brakes and tires	1,513	1,452
Other	7,564	9,675
Other accrued expenses	28,888	29,696
Aircraft and Other Flight Equipment Substantially Pledged [Member]
Property and equipment-net
Property and equipment-gross	1,582,199	1,502,940
Other Machinery and Equipment [Member]
Property and equipment-net
Property and equipment-gross	5,122	3,721
Leasehold Improvements [Member]
Property and equipment-net
Property and equipment-gross	2,797	2,754
Vehicles [Member]
Property and equipment-net
Property and equipment-gross	924	692
Building [Member]
Property and equipment-net
Property and equipment-gross	699	699
Furniture and Fixtures [Member]
Property and equipment-net
Property and equipment-gross	$ 302	$ 287

Long-Term Debt and Other Borrowings - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Total long-term debt	$ 858,145	$ 930,207
Less current portion	(165,900)	(155,170)
Less unamortized debt issuance costs	(14,822)	(14,860)
Long-term debt—excluding current portion	677,423	760,177
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member]
Debt Instrument [Line Items]
Total long-term debt		4,428
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	49,795	69,340
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2024 [Member]
Debt Instrument [Line Items]
Total long-term debt	60,761	72,438
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2027 [Member]
Debt Instrument [Line Items]
Total long-term debt	110,912	122,591
Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member]
Debt Instrument [Line Items]
Total long-term debt	191,168	209,240
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member]
Debt Instrument [Line Items]
Total long-term debt	152,945	167,269
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt	71,998	95,060
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Total long-term debt	47,309	63,403
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2022 [Member]
Debt Instrument [Line Items]
Total long-term debt		88,162
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment [Member]
Debt Instrument [Line Items]
Total long-term debt	1,659	3,318
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Total long-term debt	6,962	14,971
Notes Payable to Financial Institution Due 2020 [Member]
Debt Instrument [Line Items]
Total long-term debt	2,329	4,360
Notes Payable to Financial Institution Due 2019 [Member]
Debt Instrument [Line Items]
Total long-term debt		5,896
Other Obligations Due to Financial Institution, Collateralized by the Underlying Equipment, Due 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	8,530	$ 9,731
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2024 [Member]
Debt Instrument [Line Items]
Total long-term debt	80,153
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	65,625
Notes Payable to Financial Institution Due 2023 [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 8,000

Long-Term Debt and Other Borrowings - Schedule of Principal Maturities of Long-term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Long Term Debt By Maturity [Abstract]
2020	$ 165,900
2021	161,359
2022	152,745
2023	103,165
2024	71,033
Thereafter	203,943
Total long-term debt	$ 858,145	$ 930,207

Long-Term Debt and Other Borrowings - Additional Information (Detail) $ in Thousands							1 Months Ended	12 Months Ended
	Sep. 27, 2019 USD ($)	Sep. 25, 2019 USD ($)	Jun. 14, 2019 USD ($) Air-craft	Jan. 28, 2019 USD ($)	Jun. 28, 2018 USD ($) Air-craft shares	Jun. 27, 2018 USD ($) Air-craft	Jun. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Debt Instrument [Line Items]
Property and equipment, net								$ 1,273,585	$ 1,250,829
Long-Term Debt								858,145	930,207
Non-cash lease termination expense								9,540	$ 15,109
Warrants to purchase shares of common stock \| shares					250,000
Loss on extinguishment of debt								3,616
Payment for debt extinguishment prepayment penalties								$ 1,672
Spare Engine Facility [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 8,000
Long term debt interest rate description								Libor plus 5.25%.
Long term debt, basis spread on variable rate	5.25%
CRJ-900 [Member]
Debt Instrument [Line Items]
Refinanced debt						$ 16,000
Number of aircraft under refinanced debt \| Air-craft					6	6
Refinanced debt due period						2019
Debt instrument, face amount					$ 69,600	$ 27,500
Net cash proceeds after transaction related fees						$ 10,400
Long term debt interest rate description					LIBOR plus a spread ranging from 3.50% for the senior promissory notes to 7.50% for the subordinated promissory notes			LIBOR plus 3.50%.
Long term debt, basis spread on variable rate						3.50%
Number of aircraft purchased \| Air-craft					9
Payment for aircraft purchased					$ 76,500
Number of aircraft financed \| Air-craft					6	6
Non-cash lease termination expense					$ 15,100
Future goods and services credits					4,500
Loan forgiveness for loans					$ 5,600
Warrants to purchase shares of common stock \| shares					250,000
CRJ-700 Aircraft [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 70,000
Long term debt interest rate description			LIBOR plus 5.25%.
Long term debt, basis spread on variable rate			5.25%
Number of aircraft purchased \| Air-craft			10
Payment for aircraft purchased			$ 70,000
Non-cash lease termination expense			$ 9,500
Equipment Notes [Member]
Debt Instrument [Line Items]
Long-Term Debt								$ 191,200
Senior Notes Due 2020 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount							$ 65,800
Long term debt, basis spread on variable rate					3.50%		3.50%
Senior Notes Due 2020 [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate description									Three-month LIBOR plus 3.50%
Subordinated Notes Due 2020 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount							$ 29,800
Long term debt, basis spread on variable rate					7.50%		7.50%
Subordinated Notes Due 2020 [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate description									three-month LIBOR plus 7.50%
Term Loan
Debt Instrument [Line Items]
Debt instrument, face amount				$ 91,200
Long term debt interest rate description				LIBOR plus 3.10%
Term loan, term				5 years
Write-off of financing cost				$ 1,900
Payment for debt extinguishment prepayment penalties				$ 1,700
Term Loan \| Spare Engine Facility [Member]
Debt Instrument [Line Items]
Long term debt interest rate description				LIBOR plus 7.25%
Loss on extinguishment of debt				$ 3,600
Term Loan \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate				3.10%
Term Loan \| LIBOR [Member] \| Spare Engine Facility [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate				7.25%
Working Capital Draw Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 35,000
Long term debt interest rate description								one-month LIBOR plus 3.75%.
Long term debt, basis spread on variable rate		3.75%
Term loan, term		3 years
Aircraft and Equipment [Member] \| Pledged as Collateral [Member]
Debt Instrument [Line Items]
Property and equipment, net								$ 1,203,500

Earnings Per Share - Calculations of Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended												12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share And Equity [Abstract]
Net income	$ 12,243	$ 3,007	$ 13,249	$ 19,081	$ 19,394	$ (11,135)	$ 2,372	$ 22,624	$ 5,482	$ 15,432	$ 5,304	$ 6,610	$ 47,580	$ 33,255	$ 32,828
Basic weighted average common shares outstanding													34,764	24,826	23,201
Add: Incremental shares for:
Dilutive effect of warrants														116	93
Dilutive effect of restricted stock													300	315	76
Diluted weighted average common shares outstanding													35,064	25,257	23,370
Net income per common share
Basic	$ 0.35	$ 0.09	$ 0.38	$ 0.55	$ 0.66	$ (0.48)	$ 0.10	$ 0.97	$ 0.24	$ 0.67	$ 0.23	$ 0.28	$ 1.37	$ 1.34	$ 1.41
Diluted	$ 0.35	$ 0.09	$ 0.38	$ 0.54	$ 0.65	$ (0.48)	$ 0.10	$ 0.96	$ 0.24	$ 0.66	$ 0.23	$ 0.28	$ 1.36	$ 1.32	$ 1.40

Restatement - Summary of Basic and Diluted Net Income per Common Share Available to Common Shareholders (Detail) - $ / shares shares in Thousands	3 Months Ended												12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Line Items]
Net income per common share available to common shareholders - Basic	$ 0.35	$ 0.09	$ 0.38	$ 0.55	$ 0.66	$ (0.48)	$ 0.10	$ 0.97	$ 0.24	$ 0.67	$ 0.23	$ 0.28	$ 1.37	$ 1.34	$ 1.41
Shares used in computing net income per common share available to common shareholders - Basic													34,764	24,826	23,201
Net income per common share available to common shareholders - Diluted	$ 0.35	$ 0.09	$ 0.38	0.54	0.65	(0.48)	0.10	0.96	0.24	0.66	0.23	0.28	$ 1.36	$ 1.32	$ 1.40
Shares used in computing net income per common share available to common shareholders - Diluted													35,064	25,257	23,370
As Previously Reported
Earnings Per Share [Line Items]
Net income per common share available to common shareholders - Basic				0.80	1.04	(0.89)	0.20	2.00	0.49	1.40	0.48	0.62		$ 2.46	$ 3.01
Shares used in computing net income per common share available to common shareholders - Basic														13,516	10,919
Net income per common share available to common shareholders - Diluted				$ 0.55	$ 0.65	$ (0.89)	$ 0.10	$ 0.96	$ 0.23	$ 0.66	$ 0.23	$ 0.28		$ 1.32	$ 1.40
Shares used in computing net income per common share available to common shareholders - Diluted														25,171	23,386

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Reference 1: http://www.xbrl.org/2003/role/exampleRef
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+ Details

Common Stock - Additional Information (Detail) $ / shares in Units, $ in Millions					12 Months Ended
	Apr. 09, 2019 shares	Sep. 11, 2018 $ / shares shares	Aug. 14, 2018 USD ($) $ / shares shares	Aug. 08, 2018 shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 $ / shares shares	Jun. 28, 2018 shares
Class of Warrant or Right [Line Items]
Warrants term					5 years
Warrants of common stock exercise price \| $ / shares					$ 0.004
Maximum percentage of stock pertaining to restrictions					24.90%
Extended term of outstanding warrants expiration period					5 years
Warrants of common stock expiration date					Sep. 30, 2023
Warrants to purchase shares of common stock							250,000
Common stock, stock split					Effected a 2.5-for-1 stock split
Stock split ratio				2.5
Common stock, shares authorized				125,000,000	125,000,000	125,000,000
Preferred stock, shares authorized				5,000,000	5,000,000	5,000,000
Stock issued during period, shares, new issues		1,344,500
Common stock, no par value \| $ / shares					$ 0	$ 0
Common stock, warrants issued					3,600,953	10,614,990
2018 Equity Incentive Plan [Member]
Class of Warrant or Right [Line Items]
Increase in number of shares authorized for issuance	1,000,000
Common stock, shares authorized	3,500,000
IPO [Member]
Class of Warrant or Right [Line Items]
Stock issued during period, shares, new issues			9,630,000
Common stock, no par value \| $ / shares
Shares issued, price per share \| $ / shares			$ 12.00
Gross proceeds of initial public offering \| $			$ 115.6		$ 124.2
Net proceeds from initial public offering \| $					111.7
Underwriting discounts and commissions \| $					8.7
Offering costs \| $					$ 3.6
Underwriter Options [Member]
Class of Warrant or Right [Line Items]
Common stock, warrants issued			1,444,500
Firm Shares and Option Shares [Member]
Class of Warrant or Right [Line Items]
Shares issued, price per share \| $ / shares		$ 12.00
Purchased Directly From Company [Member]
Class of Warrant or Right [Line Items]
Stock issued during period, shares, new issues		723,985
Purchased Directly From Selling Shareholders [Member]
Class of Warrant or Right [Line Items]
Stock issued during period, shares, new issues		620,515

Income Taxes - Schedule of Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Current
Federal	$ (138)
State	341	$ 465	$ 359
Total current income tax provision (benefit)	203	465	359
Deferred
Federal	13,238	(17,308)	17,713
State	2,265	(583)	2,802
Total deferred income tax provision (benefit)	15,503	(17,891)	20,515
Provision (Benefit) for income taxes	$ 15,706	$ (17,426)	$ 20,874

Income Taxes - Schedule of Reconciliation between Effective Tax Rate Income from Continuing Operations and Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Income tax expense at federal statutory rate	$ 13,290	$ 3,878	$ 18,796
Increase (reduction) in income taxes resulting from:
State taxes, net of federal tax benefit	1,785	660	1,397
Nondeductible stock compensation expenses	(21)
Permanent items	261	63	92
Change in valuation allowances	(50)	(646)	531
US Tax Cuts and Jobs Act Impact		(22,015)
162(m) Limitation	119
Impact of changing rates on deferred tax assets	484	(773)	(353)
Expired tax attributes	111	1,088	409
Other	(273)	319	2
Provision (Benefit) for income taxes	$ 15,706	$ (17,426)	$ 20,874

Income Taxes - Schedule of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Net operating carry forwards	$ 106,645	$ 91,981
Deferred credits	1,882	2,443
Other accrued expenses	2,329	1,871
Prepaids and other	2,576	3,530
State alternative minimum tax	1	1
Other reserves and estimated losses	947	836
Operating lease	4,928	6,399
Allowance for doubtful receivables		905
Subtotal	119,308	107,966
Less: valuation allowance	(1,890)	(1,940)
Total net deferred tax assets	117,418	106,026
Intangibles	(2,204)	(2,613)
Property and equipment	(170,517)	(143,210)
Total deferred tax liabilities	(172,721)	(145,823)
Net deferred tax liability	$ (55,303)	$ (39,797)

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Taxes [Line Items]
Operating loss carryforwards, valuation allowance	$ 1,900	$ 1,900	$ 1,900
Unrecognized tax benefits if unrecognized, the balance of uncertain tax benefit would affect the effective tax rate	4,700	$ 4,700	$ 4,700	$ 7,500
Federal corporate tax rate		21.00%	21.00%
Discrete net tax benefit in connection with initial analysis of tax act			$ 22,400
Decrease in net deferred tax liabilities excluding valuation allowance			22,000
Estimated increase to valuation allowance			500
Adjustment to deferred income tax benefit	900		21,500
AMT credits	$ 2,500		2,500
Provisional tax expense (benefit)		$ 15,706	$ (17,426)	$ 20,874
AMT Credit Carryover [Member]
Income Taxes [Line Items]
Provisional tax expense (benefit)		(100)
Domestic Tax Authority [Member] \| 2027-2037 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		478,300
State and Local Jurisdiction [Member] \| 2019-2038 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		$ 228,300
Minimum [Member] \| Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2027
Minimum [Member] \| State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2020
Maximum [Member] \| Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2037
Maximum [Member] \| State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year		2039

Share-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands				1 Months Ended			12 Months Ended				72 Months Ended
	Sep. 11, 2018	Aug. 14, 2018	Oct. 17, 2017	Apr. 30, 2019	Aug. 31, 2018	Jul. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2014	Sep. 30, 2019	Apr. 09, 2019	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, new issues	1,344,500
Unrecognized compensation cost related to unvested share-based compensation arrangements							$ 5,900				$ 5,900
Unrecognized compensation cost, period for recognition							1 year 6 months
Share-based compensation expense							$ 5,500	$ 12,900	$ 2,300
Repurchased shares, value							$ 1,872	$ 7,709	$ 1,043
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, new issues								10,354,018
Repurchased shares, shares							205,235	438,541
Repurchased shares, value							$ 1,900	$ 5,000
IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period, shares, new issues		9,630,000
Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period							1 year
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested								622,238	1,460,812		3,687,218
Number of shares cancelled								517,775
Number of shares unvested								0	1,140,013				2,223,333
Number of shares granted								0	384,160		4,204,993
Number of shares authorized										5,000,000
Shares vesting period										3 years
Shares expiration period										10 years
Number of shares exercised											2,088,333
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested											44,623
Number of shares granted											536,538
Number of shares authorized			1,250,000
Shares vesting period			3 years
Restricted Stock Units [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period							3 years
Restricted Stock Units [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period							5 years
Restricted Stock Award \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period							3 years
Restricted Stock Award \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period							5 years
2018 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized												3,500,000
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested				1,700,104			701,582	32,500	0
Stock issued during period, shares, new issues						2,249,147
Number of shares cancelled				22,995	966,022	491,915	22,995	0
Unvested restricted shares issued						491,198
Number of shares unvested							847,974	1,250,625	0		847,974		0
Number of shares granted		1,266,034		2,571,073			321,926		0
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized				2,500,000
2018 Equity Incentive Plan [Member] \| Restricted Stock [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized				3,500,000
2018 Equity Incentive Plan [Member] \| Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested					1,598,885	966,022
Stock issued during period, shares, new issues						1,266,034
Number of shares cancelled					300,012
Number of shares unvested						300,012
2018 Equity Incentive Plan [Member] \| Stock Appreciation Rights [Member] \| IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested restricted shares issued					517,775
2018 Equity Incentive Plan [Member] \| Restricted Stock Units [Member] \| IPO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares cancelled					491,915
2011 Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested						1,978,550
Number of shares cancelled						470,355
Number of shares granted						2,448,905
2017 Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares vested						10,412
Number of shares cancelled						20,843
Number of shares granted						31,255

Share-Based Compensation - Schedule of Restricted Stock Activity (Detail) - Restricted Stock [Member] - $ / shares		1 Months Ended			12 Months Ended
	Aug. 14, 2018	Apr. 30, 2019	Aug. 31, 2018	Jul. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
2011 and 2017 Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance					0	775,753	757,328
Number of Shares, Granted						0	251,615
Number of Shares, Vested						(284,555)	(233,190)
Number of Shares, Cancelled						(491,198)
Number of Shares, Forfeited							0
Number of Shares, Unvested, Ending Balance						0	775,753
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance					$ 0	$ 5.22	$ 5.40
Weighted-Average Grant Date Fair Value, Granted						0	4.54
Weighted-Average Grant Date Fair Value, Vested						5.26	5.06
Weighted-Average Grant Date Fair Value, Forfeited							0
Weighted-Average Grant Date Fair Value, Cancelled						5.20
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance						$ 0	$ 5.22
2018 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance					1,250,625	0	0
Number of Shares, Granted	1,266,034	2,571,073			321,926		0
Exchanged Restricted Shares						491,198
Exchanged Phantom Stock						491,915
Exchanged SARs						1,266,034
Exchanged SARs vested prior to exchange						(966,022)
Number of Shares, Vested		(1,700,104)			(701,582)	(32,500)	0
Number of Shares, Cancelled		(22,995)	(966,022)	(491,915)	(22,995)	0
Number of Shares, Forfeited							0
Number of Shares, Unvested, Ending Balance					847,974	1,250,625	0
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance					$ 9.59	$ 0	$ 0
Weighted-Average Grant Date Fair Value, Granted					8.94		0
Exchanged Restricted Shares						5.20
Exchanged Phantom Stock						12.00
Exchanged SARs						12.00
Exchanged SARs vested prior to exchange						12.00
Weighted-Average Grant Date Fair Value, Vested					9.25	2.00	0
Weighted-Average Grant Date Fair Value, Forfeited							0
Weighted-Average Grant Date Fair Value, Cancelled					12.00	0
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance					$ 9.56	$ 9.59	$ 0

Share-Based Compensation - Schedule of SARs Activity (Detail) - Stock Appreciation Rights [Member] - $ / shares	12 Months Ended		72 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance	1,140,013	2,223,333
Number of Shares, Granted	0	384,160	4,204,993
Number of Shares, Vested	(622,238)	(1,460,812)	(3,687,218)
Number of Shares, Cancelled	(517,775)
Number of Shares, Forfeited	0	(6,668)
Number of Shares, Unvested, Ending Balance	0	1,140,013
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance	$ 0	$ 1.19
Weighted-Average Grant Date Fair Value, Granted	0	0
Weighted-Average Grant Date Fair Value, Vested	0	1.96
Weighted-Average Grant Date Fair Value, Cancelled	8.69
Weighted-Average Grant Date Fair Value, Forfeited	0	0
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance	$ 0	$ 0

Share-Based Compensation - Schedule of Phantom Stock Activity (Detail) - Phantom Stock [Member]	12 Months Ended
	Sep. 30, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance \| shares	0
Number of Shares, Granted \| shares	536,538
Number of Shares, Vested \| shares	(44,623)
Number of Shares, Cancelled \| shares	(491,915)
Number of Shares, Unvested, Ending Balance \| shares	0
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance \| $ / shares	$ 0
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	6.14
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	7.30
Weighted-Average Grant Date Fair Value, Cancelled \| $ / shares	12.00
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance \| $ / shares	$ 0

Employee Stock Purchase Plan - Additional Information (Detail) - 2019 ESPP [Member]	12 Months Ended
	Sep. 30, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares, discount rate	10.00%
Number of ordinary shares issued	0
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Eligible employees contribution from their eligible compensation during each semi annual	1.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Eligible employees contribution from their eligible compensation during each semi annual	15.00%
Number of ordinary shares issued	500,000

Commitments - Schedule of Future Minimum Lease Payments (Detail) $ in Thousands	Sep. 30, 2019 USD ($)
Operating Leased Assets [Line Items]
2020	$ 47,814
2021	46,007
2022	31,090
2023	13,726
2024	13,185
Thereafter	1,368
Total	153,190
Aircraft [Member]
Operating Leased Assets [Line Items]
2020	44,231
2021	44,314
2022	29,751
2023	12,418
2024	11,849
Total	142,563
Other [Member]
Operating Leased Assets [Line Items]
2020	3,583
2021	1,693
2022	1,339
2023	1,308
2024	1,336
Thereafter	1,368
Total	$ 10,627

Selected Consolidated Quarterly Financial Data (Unaudited) - Schedule of Selected Consolidated Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Quarterly Financial Information Disclosure [Line Items]
Total operating revenues	$ 187,830	$ 180,224	$ 177,147	$ 178,156	$ 177,532	$ 171,739	$ 167,640	$ 164,684	$ 157,293	$ 166,952	$ 159,096	$ 160,235	$ 723,357	$ 681,595	$ 643,576
Operating income	30,453	17,077	34,377	39,230	41,784	(508)	16,349	15,023	22,691	36,360	20,405	20,838	121,137	72,648	100,294
Net income	$ 12,243	$ 3,007	$ 13,249	$ 19,081	$ 19,394	$ (11,135)	$ 2,372	$ 22,624	$ 5,482	$ 15,432	$ 5,304	$ 6,610	$ 47,580	$ 33,255	$ 32,828
Net income per common share
Basic	$ 0.35	$ 0.09	$ 0.38	$ 0.55	$ 0.66	$ (0.48)	$ 0.10	$ 0.97	$ 0.24	$ 0.67	$ 0.23	$ 0.28	$ 1.37	$ 1.34	$ 1.41
Diluted	$ 0.35	$ 0.09	$ 0.38	$ 0.54	$ 0.65	$ (0.48)	$ 0.10	$ 0.96	$ 0.24	$ 0.66	$ 0.23	$ 0.28	$ 1.36	$ 1.32	$ 1.40
Contract Revenue [Member]
Quarterly Financial Information Disclosure [Line Items]
Total operating revenues	$ 172,248	$ 170,366	$ 169,771	$ 170,449	$ 168,444	$ 159,916	$ 156,515	$ 154,389	$ 151,575	$ 157,411	$ 154,210	$ 155,502	$ 682,834	$ 639,264	$ 618,698

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Selected Consolidated Quarterly Financial Data (Unaudited) - Summary of Basic and Diluted Net Income (Loss) per Common Share Available to Common Shareholders (Detail) - $ / shares	3 Months Ended												12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Net income per common share
Net income per common share available to common shareholders - Basic	$ 0.35	$ 0.09	$ 0.38	$ 0.55	$ 0.66	$ (0.48)	$ 0.10	$ 0.97	$ 0.24	$ 0.67	$ 0.23	$ 0.28	$ 1.37	$ 1.34	$ 1.41
Net income per common share available to common shareholders - Diluted	$ 0.35	$ 0.09	$ 0.38	0.54	0.65	(0.48)	0.10	0.96	0.24	0.66	0.23	0.28	$ 1.36	1.32	1.40
As Previously Reported
Net income per common share
Net income per common share available to common shareholders - Basic				0.80	1.04	(0.89)	0.20	2.00	0.49	1.40	0.48	0.62		2.46	3.01
Net income per common share available to common shareholders - Diluted				$ 0.55	$ 0.65	$ (0.89)	$ 0.10	$ 0.96	$ 0.23	$ 0.66	$ 0.23	$ 0.28		$ 1.32	$ 1.40

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

Subsequent Events - Additional Information (Detail)					1 Months Ended	12 Months Ended
Subsequent Events - Additional Information (Detail)	Jan. 02, 2020 Air-craft	Dec. 11, 2019 Engine	Nov. 26, 2019 Air-craft	Nov. 25, 2019 Air-craft	Aug. 28, 2019 Air-craft	Sep. 30, 2019 Air-craft
Subsequent Event [Line Items]
Number of aircrafts operated						145
Number of leased aircraft						18
Number of additional aircraft permanently withdrawn due to company's failure to meet certain performance metrics					2
American Airlines Inc. [Member] \| Scenario Forecast [Member]
Subsequent Event [Line Items]
Number of deferred aircraft elected to remove	1
E-175 Aircraft [Member]
Subsequent Event [Line Items]
Number of aircrafts operated						60
CRJ-700 Aircraft [Member]
Subsequent Event [Line Items]
Number of aircrafts operated						20
Subsequent Event [Member] \| American Airlines Inc. [Member]
Subsequent Event [Line Items]
Number of additional aircraft permanently withdrawn due to company's failure to meet certain performance metrics				2
Subsequent Event [Member] \| E-175LL Aircraft [Member]
Subsequent Event [Line Items]
Number of additional aircrafts			20
Number of years in operation			12 years
Number of aircrafts operated			80
Termination of aircraft operation, description			Commencing five (5) years after the actual in-service date, United has the right to remove the new E175LL aircraft from service by giving the Company 90 days or more notice, subject to certain conditions, including the payment of certain wind-down expenses plus, if removed prior to the ten (10) year anniversary of the in-service date, certain accelerated margin payments.
Subsequent Event [Member] \| E-175 Aircraft [Member]
Subsequent Event [Line Items]
Number of additional aircrafts			18
Subsequent Event [Member] \| E-175 Aircraft [Member] \| United [Member]
Subsequent Event [Line Items]
Number of aircrafts operated			42
Aircraft lease extension period			5 years
Subsequent Event [Member] \| CRJ-700 Aircraft [Member]
Subsequent Event [Line Items]
Number of leased aircraft			20
Aircraft lease term			7 years
Subsequent Event [Member] \| CRJ-700 Aircraft [Member] \| United [Member]
Subsequent Event [Line Items]
Aircraft lease term			7 years
Right to purchase aircraft at fair market value			20
Subsequent Event [Member] \| CF34-8C5 Engine [Member]
Subsequent Event [Line Items]
Number of new spare engines to be acquired \| Engine		20
New spare engines delivery month and year description		The Company expects to take delivery of the engines between August 2020 and December 2021.

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Contract Revenue [Member]
Revenue from related party	$ 376,506	$ 359,467	$ 354,614
Pass Through and Other [Member]
Revenue from related party	$ 7,257	$ 6,628	$ 7,920

Intangible Assets - Information About Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Intangible Assets Net Excluding Goodwill [Abstract]
Customer relationship	$ 43,800	$ 43,800
Accumulated amortization	(34,268)	(32,459)
Total	$ 9,532	$ 11,341

Commitments - Additional Information (Detail) $ in Millions	12 Months Ended
Commitments - Additional Information (Detail) $ in Millions	Sep. 30, 2019 USD ($) Air-craft	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Operating Leased Assets [Line Items]
Number of leased aircraft \| Air-craft	18
Aggregate rental expense under all operating aircraft, equipment and facility leases \| $	$ 72.8	$ 85.9	$ 83.8
Aircraft [Member]
Operating Leased Assets [Line Items]
Operating leases remaining term	4 years 6 months
Headquarters and other facility [Member]
Operating Leased Assets [Line Items]
Operating leases remaining term	6 years 2 months 12 days

Long-Term Debt and Other Borrowings - Schedule of Long-term Debt (Parenthetical) (Detail)			1 Months Ended						12 Months Ended
	Jun. 28, 2018 USD ($) Air-craft	Jun. 27, 2018 USD ($) Air-craft	Sep. 27, 2019 USD ($)	Jun. 30, 2019 USD ($) Airfleet	Jan. 31, 2019 USD ($)	Jun. 30, 2018 USD ($) Air-craft	Feb. 28, 2018 Engine	Dec. 31, 2017 USD ($) Air-craft	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($) Air-craft	Sep. 30, 2015 USD ($) Air-craft	Sep. 30, 2007 USD ($) Airfleet	Sep. 30, 2005 USD ($) Airfleet	Sep. 30, 2004 USD ($) Airfleet	Sep. 30, 2014 USD ($) Airfleet
Debt Instrument [Line Items]
Imputed interest							9.128%
Number of spare engines leased \| Engine							2
CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 69,600,000	$ 27,500,000
Long term debt interest rate description	LIBOR plus a spread ranging from 3.50% for the senior promissory notes to 7.50% for the subordinated promissory notes								LIBOR plus 3.50%.
Long term debt basis spread on variable rate		3.50%
Number of aircraft financed \| Air-craft	6	6
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2019	2019
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Number of aircraft refinanced \| Airfleet														5	9
Debt instrument, face amount														$ 118,000,000
Long term debt interest rate description									London InterBank Offered Rate ("LIBOR"), plus 3%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate														3.00%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member] \| CRJ-700 [Member]
Debt Instrument [Line Items]
Number of aircraft refinanced \| Airfleet															5
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member] \| Five C- R- J-700 and Nine C- R- J-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount															$ 254,700,000
Long term debt interest rate description									monthly LIBOR plus 3%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2019 [Member] \| Five C- R- J-700 and Nine C- R- J-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate															3.00%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2022	2022
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Number of aircraft refinanced \| Airfleet													3
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| CRJ-700 [Member]
Debt Instrument [Line Items]
Number of aircraft refinanced \| Airfleet													3
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| Three C- R- J-900 and Three C- R- J-700 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount													$ 120,300,000
Long term debt interest rate description									monthly LIBOR plus 2.25%
Long term debt interest rate percentage									4.27%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| Three C- R- J-900 and Three C- R- J-700 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate													2.25%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| Ten C- R- J-900 Aircraft [Member]
Debt Instrument [Line Items]
Debt instrument, face amount																$ 88,400,000
Long term debt interest rate description									LIBOR plus a spread ranging from 1.95% to 7.25%
Number of aircraft financed \| Airfleet																10
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| Ten C- R- J-900 Aircraft [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									3.97%							1.95%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| Ten C- R- J-900 Aircraft [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									9.27%							7.25%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2024 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2024	2024
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2024 [Member] \| Eight C- R- J-900 Aircraft [Member]
Debt Instrument [Line Items]
Debt instrument, face amount																$ 114,500,000
Number of aircraft financed \| Airfleet																8
Long term debt interest rate percentage																5.00%
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2027 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2027	2027
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2027 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 170,200,000
Number of aircraft financed \| Air-craft												7
Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2028	2028
Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member] \| Ten E-175 Aircraft [Member]
Debt Instrument [Line Items]
Debt instrument, face amount											$ 246,000,000
Number of aircraft financed \| Air-craft											10
Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member] \| Ten E-175 Aircraft [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									4.75%
Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member] \| Ten E-175 Aircraft [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									6.25%
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2028	2028
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member] \| Eight E-175 Aircraft [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Number of aircraft refinanced \| Air-craft											8
Debt instrument, face amount											$ 195,300,000
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2022	2022
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2022	2022
Number of aircraft refinanced \| Air-craft						6		9
Debt instrument, face amount						$ 27,500,000		$ 74,900,000
Number of aircraft financed \| Air-craft						9
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| CRJ-900 [Member] \| Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 69,600,000
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2022 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2022	2022
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2022 [Member] \| Flight Equipment [Member]
Debt Instrument [Line Items]
Debt instrument, face amount										$ 99,100,000
Long term debt interest rate description									monthly LIBOR plus 7.25%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2022 [Member] \| Flight Equipment [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate										7.25%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2020	2020
Debt instrument, face amount												$ 8,300,000
Long term debt interest rate percentage												5.163%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2020	2020
Debt instrument, face amount										$ 11,900,000	$ 11,900,000
Long term debt interest rate description									Three-month LIBOR plus a spread ranging from 2.93% to 2.96%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									5.02%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									5.05%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate										2.93%	2.93%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate										2.96%	2.96%
Notes Payable to Financial Institution Due 2020 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2020	2020
Notes Payable to Financial Institution Due 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument, face amount											$ 10,200,000	$ 10,200,000
Long term debt interest rate description									three-month LIBOR plus 3.07%
Long term debt interest rate percentage									5.16%
Notes Payable to Financial Institution Due 2020 [Member] \| Flight Equipment Maintenance [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage											3.07%	3.07%
Notes Payable to Financial Institution Due 2019 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2019	2019
Notes Payable to Financial Institution Due 2019 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument, face amount										$ 25,000,000
Long term debt interest rate description									Three-month LIBOR plus 3.30%
Long term debt basis spread on variable rate										3.30%
Other Obligations Due to Financial Institution, Collateralized by the Underlying Equipment, Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2023	2023
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2024 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2024	2024
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2024 [Member] \| Flight Equipment [Member]
Debt Instrument [Line Items]
Debt instrument, face amount					$ 91,200,000
Long term debt interest rate description									monthly LIBOR plus 3.10%
Long term debt interest rate percentage									5.12%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2024 [Member] \| Flight Equipment [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate					3.10%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2023	2023
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member] \| CRJ-700 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 70,000,000
Long term debt interest rate description									monthly LIBOR plus 5.25%
Long term debt interest rate percentage									7.27%
Number of aircraft financed \| Airfleet				10
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member] \| CRJ-700 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate				5.25%
Notes Payable to Financial Institution Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year									2023	2023
Debt instrument, face amount			$ 8,000,000						$ 8,000
Long term debt interest rate description									monthly LIBOR plus 5.25%
Long term debt basis spread on variable rate			5.25%
Long term debt interest rate percentage									7.27%
Senior Notes Due Two Thousand Twenty Seven [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 151,000,000
Long term debt interest rate description									monthly LIBOR plus 2.71%
Long term debt interest rate percentage									4.73%
Senior Notes Due Two Thousand Twenty Seven [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate												2.71%
Subordinated Notes Due Two Thousand Twenty Seven [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Imputed interest												6.25%
Debt discount												$ 8,100,000
Senior Notes Due 2008 [Member] \| Eight E-175 Aircraft [Member]
Debt Instrument [Line Items]
Long term debt interest rate description									Three-month LIBOR plus a spread ranging from 2.20% to 2.32%
Senior Notes Due 2008 [Member] \| Eight E-175 Aircraft [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, face amount											$ 172,000,000
Long term debt interest rate percentage									4.29%
Senior Notes Due 2008 [Member] \| Eight E-175 Aircraft [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									4.41%
Senior Notes Due 2008 [Member] \| Eight E-175 Aircraft [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate											2.20%
Senior Notes Due 2008 [Member] \| Eight E-175 Aircraft [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate											2.32%
Subordinated Notes Due 2008 [Member] \| Eight E-175 Aircraft [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									4.50%
Senior Notes due Two Thousand Twenty Two [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount								$ 46,900,000
Long term debt interest rate description									three-month LIBOR plus 3.50
Long term debt interest rate percentage									5.59%
Senior Notes due Two Thousand Twenty Two [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt basis spread on variable rate								3.50%
Subordinated Notes DueTwoThousandTwentyTwo [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Long term debt interest rate description									three-month LIBOR plus 4.50%
Long term debt interest rate percentage									6.59%
Subordinated Notes DueTwoThousandTwentyTwo [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage								4.50%
Senior Notes Due 2020 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 65,800,000
Long term debt basis spread on variable rate	3.50%					3.50%
Long term debt interest rate percentage										5.59%
Senior Notes Due 2020 [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate description										Three-month LIBOR plus 3.50%
Subordinated Notes Due 2020 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 29,800,000
Long term debt basis spread on variable rate	7.50%					7.50%
Long term debt interest rate percentage										9.59%
Subordinated Notes Due 2020 [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate description										three-month LIBOR plus 7.50%