0001564590-21-026250 | 10-Q | XBRL Viewer

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Document and Entity Information	6 Months Ended
Document and Entity Information	Mar. 31, 2021 shares
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Trading Symbol	MESA
Title of 12(b) Security	Common Stock, no par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	NV
Entity File Number	001-38626
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, Postal Zip Code	85008
City Area Code	602
Local Phone Number	685-4000
Entity Address, State or Province	AZ
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 Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding	35,700,161

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Current assets:
Cash and cash equivalents	$ 147,867	$ 99,395
Restricted cash	3,351	3,446
Receivables, net	13,867	13,712
Expendable parts and supplies, net	23,044	22,971
Prepaid expenses and other current assets	8,956	16,067
Total current assets	197,085	155,591
Property and equipment, net	1,180,684	1,212,415
Intangibles, net	7,412	8,032
Lease and equipment deposits	8,242	1,899
Operating lease right-of-use assets	105,521	123,251
Other assets	20,647	742
Total assets	1,519,591	1,501,930
Current liabilities:
Current portion of long-term debt and financing leases	103,980	189,268
Current portion of deferred revenue	4,356	9,389
Current maturities of operating leases	44,016	43,932
Accounts payable	70,012	53,229
Accrued compensation	10,449	12,030
Other accrued expenses	28,610	45,478
Total current liabilities	261,423	353,326
Noncurrent liabilities:
Long-term debt and financing leases, excluding current portion	600,058	542,456
Noncurrent operating lease liabilities	38,405	62,531
Deferred credits	7,442	5,705
Deferred income taxes	70,929	64,275
Deferred revenue, net of current portion	29,502	14,369
Other noncurrent liabilities	20,988	1,409
Total noncurrent liabilities	767,324	690,745
Total liabilities	1,028,747	1,044,071
Commitments and contingencies (Note 14)
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; 35,700,161 (2021) and 35,526,918 (2020) shares issued and outstanding, 4,899,497 (2021) and 0 (2020) warrants issued and outstanding	255,950	242,772
Retained earnings	234,894	215,087
Total stockholders' equity	490,844	457,859
Total liabilities and stockholders' equity	$ 1,519,591	$ 1,501,930

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Sep. 30, 2020
Statement Of Financial Position [Abstract]
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	35,700,161	35,526,918
Common stock, shares outstanding	35,700,161	35,526,918
Common stock, warrants issued	4,899,497	0
Common stock, warrants outstanding	4,899,497	0

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Operating revenues:
Total operating revenues	$ 97,280	$ 179,896	$ 247,651	$ 363,931
Operating expenses:
Flight operations	37,403	52,891	74,367	105,535
Fuel	198	188	588	358
Maintenance	51,773	64,335	104,637	122,430
Aircraft rent	9,992	12,285	20,040	23,614
Aircraft and traffic servicing	743	1,336	1,644	2,400
General and administrative	11,164	14,500	24,237	27,496
Depreciation and amortization	20,705	20,469	41,175	41,021
Lease termination	4,508		4,508
Government grant recognition	(55,967)		(67,278)
Total operating expenses	80,519	166,004	203,918	322,854
Operating income	16,761	13,892	43,733	41,077
Other (expenses) income, net:
Interest expense	(8,755)	(11,673)	(17,837)	(24,300)
Interest income	79	36	205	94
Other (expense) income, net	(506)	937	417	641
Total other (expense), net	(9,182)	(10,700)	(17,215)	(23,565)
Income before taxes	7,579	3,192	26,518	17,512
Income tax expense	1,890	1,307	6,711	4,842
Net income and comprehensive income	$ 5,689	$ 1,885	$ 19,807	$ 12,670
Net income per share attributable to common shareholders
Basic	$ 0.16	$ 0.05	$ 0.56	$ 0.36
Diluted	$ 0.14	$ 0.05	$ 0.52	$ 0.36
Weighted-average common shares outstanding
Basic	35,628	35,141	35,579	35,082
Diluted	39,432	35,265	38,382	35,220
Contract Revenue [Member]
Operating revenues:
Total operating revenues	$ 81,712	$ 165,781	$ 208,870	$ 337,580
Pass Through and Other [Member]
Operating revenues:
Total operating revenues	$ 15,568	$ 14,115	$ 38,781	$ 26,351

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Revision of Prior Period Accounting Standards Update Adjustment [Member]	Common Stock [Member]	Number of Warrants [Member]	Common Stock and Additional Paid-In Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Revision of Prior Period Accounting Standards Update Adjustment [Member]
Beginning balance at Sep. 30, 2019	$ 425,868				$ 238,504	$ 187,364
Beginning balance (ASU 2018-09 [Member]) at Sep. 30, 2019		$ 259					$ 259
Beginning balance, shares at Sep. 30, 2019			31,413,287	3,600,953
Stock compensation expense	1,320				1,320
Repurchased shares and warrants	(41)				(41)
Repurchased shares and warrants, shares			(5,558)
Warrants converted to common stock			1,612,481	(1,612,481)
Restricted shares issued, shares			18,916
Net income	10,785					10,785
Ending balance at Dec. 31, 2019	438,191				239,783	198,408
Ending balance, shares at Dec. 31, 2019			33,039,126	1,988,472
Beginning balance at Sep. 30, 2019	425,868				238,504	187,364
Beginning balance (ASU 2018-09 [Member]) at Sep. 30, 2019		$ 259					$ 259
Beginning balance, shares at Sep. 30, 2019			31,413,287	3,600,953
Net income	12,670
Ending balance at Mar. 31, 2020	441,352				241,059	200,293
Ending balance, shares at Mar. 31, 2020			35,194,902
Beginning balance at Dec. 31, 2019	438,191				239,783	198,408
Beginning balance, shares at Dec. 31, 2019			33,039,126	1,988,472
Stock compensation expense	1,193				1,193
Repurchased shares and warrants	(160)				(160)
Repurchased shares and warrants, shares			(18,244)
Warrants converted to common stock			1,988,472	(1,988,472)
Restricted shares issued, shares			141,614
Employee share purchases	243				243
Employee share purchases, shares			43,934
Net income	1,885					1,885
Ending balance at Mar. 31, 2020	441,352				241,059	200,293
Ending balance, shares at Mar. 31, 2020			35,194,902
Beginning balance at Sep. 30, 2020	457,859				242,772	215,087
Beginning balance, shares at Sep. 30, 2020			35,526,918
Stock compensation expense	850				850
Repurchased shares and warrants	(19)				(19)
Repurchased shares and warrants, shares			(2,256)
Restricted shares issued, shares			7,500
Issuance of warrants, net of issuance costs	11,489				11,489
Issuance of warrants, net of issuance costs, shares				4,899,497
Net income	14,118					14,118
Ending balance at Dec. 31, 2020	484,297				255,092	229,205
Ending balance, shares at Dec. 31, 2020			35,532,162	4,899,497
Beginning balance at Sep. 30, 2020	457,859				242,772	215,087
Beginning balance, shares at Sep. 30, 2020			35,526,918
Repurchased shares and warrants			$ (200)
Net income	19,807
Ending balance at Mar. 31, 2021	490,844				255,950	234,894
Ending balance, shares at Mar. 31, 2021			35,700,161	4,899,497
Beginning balance at Dec. 31, 2020	484,297				255,092	229,205
Beginning balance, shares at Dec. 31, 2020			35,532,162	4,899,497
Stock compensation expense	808				808
Repurchased shares and warrants	(157)				(157)
Repurchased shares and warrants, shares			(14,680)
Restricted shares issued, shares			124,609
Employee share purchases	207				207
Employee share purchases, shares			58,070
Net income	5,689					5,689
Ending balance at Mar. 31, 2021	$ 490,844				$ 255,950	$ 234,894
Ending balance, shares at Mar. 31, 2021			35,700,161	4,899,497

Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 19,807,000	$ 12,670,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	41,175,000	41,021,000
Stock compensation expense	1,658,000	2,513,000
Deferred income taxes	6,654,000	4,490,000
Amortization of deferred credits	(2,258,000)	(2,041,000)
Amortization of debt discount and issuance costs	4,994,000	2,149,000
Gain on extinguishment of debt	(950,000)
Loss on disposal of assets	25,000	514,000
Provision for obsolete expendable parts and supplies	22,000	306,000
Lease termination	4,508,000
Changes in assets and liabilities:
Receivables	(155,000)	9,019,000
Expendable parts and supplies	(84,000)	(1,382,000)
Prepaid expenses and other current assets	(1,988,000)	97,000
Accounts payable	15,470,000	(602,000)
Deferred revenue	10,099,000
Accrued liabilities	(14,091,000)	2,122,000
Change in operating lease right-of- use assets	(6,311,000)	(5,674,000)
Net cash provided by operating activities	78,575,000	65,202,000
Cash flows from investing activities:
Capital expenditures	(5,261,000)	(12,968,000)
Net returns (payments) on equipment & other deposits	(6,414,000)	(11,805,000)
Net cash used in investing activities	(11,675,000)	(24,773,000)
Cash flows from financing activities:
Proceeds from long-term debt	195,000,000	23,000,000
Principal payments on long-term debt and financing leases	(212,020,000)	(79,395,000)
Payments of debt and warrant issuance	(1,326,000)	(494,000)
Repurchase of stock	(176,000)	(201,000)
Net cash used in financing activities	(18,522,000)	(57,090,000)
Net change in cash, cash equivalents and restricted cash	48,378,000	(16,661,000)
Cash, cash equivalents and restricted cash at beginning of period	102,841,000	72,501,000
Cash, cash equivalents and restricted cash at end of period	151,219,000	55,840,000
Supplemental cash flow information
Cash paid for interest	16,922,000	22,402,000
Cash paid for income taxes, net	49,000	45,000
Operating lease payments in operating cash flows	25,716,000	26,240,000
Supplemental non-cash transactions
Warrants received from Archer Aviation Inc. ("Archer")	16,400
Right-of-use assets (disposed) obtained	(320,000)	145,627,000
Debt issuance cost related to loan agreement with US Department of Treasury	$ (1,887,000)
Accrued capital expenditures		$ 98,000

Organization and Operations

6 Months Ended

Mar. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Operations

1.	Organization and Operations

About Mesa Air Group, Inc.

Headquartered in Phoenix, Arizona, Mesa Air Group, Inc. ("Mesa" or the "Company") is a holding company whose principal subsidiary, Mesa Airlines, Inc. ("Mesa Airlines"), operates as a regional air carrier providing scheduled flight service to 112 cities in 38 states, the District of Columbia, and Mexico as well as cargo flight services originating from Cincinnati/Northern Kentucky International Airport. As of March 31, 2021, Mesa operated a fleet of 163 aircraft with approximately 440 daily departures and 3,111 employees. Mesa operates all of its flights on behalf of major partners as either American Eagle, United Express, or DHL Express flights pursuant to the terms of the Capacity Purchase Agreements (“CPAs”) entered into with American Airlines, Inc. (“American”) and United Airlines, Inc. (“United”) and Flight Services Agreement (“FSA”) with DHL Network Operations (USA), Inc. (“DHL”).

The financial arrangements between the Company and its major partners involve a revenue-guarantee arrangement whereby the major partner pays fixed-fees for each aircraft under contract, departure, flight hour (measured from takeoff to landing, excluding taxi time) or block hour (measured from takeoff to landing, including taxi time), and reimbursement of certain direct operating expenses in exchange for providing flight services. The major partners also pay certain expenses directly to suppliers, such as fuel, ground operations and landing fees. Under the terms of these capacity purchase agreements, the major airline controls route selection, pricing and seat inventories, reducing the Company's exposure to fluctuations in passenger traffic, fare levels, and fuel prices.

American Capacity Purchase Agreement

As of March 31, 2021, the Company operated 45 CRJ-900 aircraft under the American Capacity Purchase Agreement. In exchange for providing flight services, 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 during each month. In addition, we may also receive incentives or incur penalties based upon our operational performance, including controllable on-time departures and controllable completion percentages. American also reimburses us for certain costs on an actual basis, including passenger liability and hull insurance and aircraft property taxes. Other expenses, including fuel and certain landing fees, are directly paid to suppliers by American. In addition, American also provides, at no cost to us, certain ground handling and customer service functions, as well as airport-related facilities and gates at American hubs and cities where we operate.

On November 19, 2020, we entered into an Amended and Restated American Capacity Purchase Agreement (the “Amended and Restated American Capacity Purchase Agreement”). The Amended and Restated American Capacity Purchase Agreement included the following amendments to the existing CPA:

•

Extended the CPA for a five-year term, commencing January 1, 2021 to December 31, 2025;

•

Reduced the number of aircraft operated under the agreement to 40 CRJ-900 aircraft;

•

Provided American the option in its sole discretion to withdraw up to: (a) 10 aircraft during calendar year 2021, provided that for the 6-month period ending June 30, 2021, American may only exercise this right if the number of mainline narrow body aircraft in American’s fleet has been reduced by a specified number of aircraft during such period, (b) 5 aircraft during each of calendar years 2022 and 2023, and (c) during the period from January 1, 2024 to July 31, 2024. American can remove the first 20 aircraft to the extent not otherwise removed in 2021 – 2023, and thereafter they have the right to remove the last 20 aircraft;

On December 22, 2020, we entered into Amendment No. 1 (“Amendment No. 1”) to the Amended and Restated American Capacity Purchase Agreement. The amendments in Amendment No. 1 reflect the following:

•

Addition of CRJ-900 aircraft to the Amended and Restated American Capacity Purchase Agreement (collectively, the “Incremental Aircraft”) in accordance with the following schedule: (i) 3 aircraft, commencing January 5, 2021 to March 3, 2021, and (ii) increasing to a total of 5 aircraft, commencing March 4, 2021. The term of the Incremental Aircraft will be determined by American in its sole discretion to withdraw any Incremental Aircraft upon 60 days’ prior notice. American may specify one or more dates for the withdrawal of such Incremental Aircraft.

On April 9, 2021, we entered into Amendment No. 2 (“Amendment No. 2”) to the Amended and Restated American Capacity Purchase Agreement. The amendments in Amendment No. 2 reflect the following:

•

Addition of CRJ-900 aircraft to the American CPA (collectively, the “Incremental Aircraft”) in accordance with the following schedule: (i) 5 aircraft, commencing March 4, 2021 to May 5, 2021, and (ii) decreasing to a total of 3 aircraft, commencing May 6, 2021 to June 2, 2021, and (iii) increasing to a total of 5 aircraft commencing on June 3, 2021 until August 17, 2021. The term of the Incremental Aircraft will be determined by American in its sole discretion to withdraw any Incremental Aircraft upon 60 days’ prior notice. American may specify one or more dates for the withdrawal of such Incremental Aircraft.

On April 19, 2021, we entered into Amendment No. 3 (“Amendment No. 3”) to the Amended and Restated American Capacity Purchase Agreement. The amendments in Amendment No. 3 reflect the following:

•

A temporary reduction in rates for fixed amount per month, per aircraft and per block rates for the period December 2020 to March 2021. The basis for the reduction is lower labor costs due to the grant received under the Payroll Support Program Extension (PSP2).

•

Agreement to a temporary reduction in rates if Mesa receives grants under the Payroll Support Program Extension (PSP3).

Our Amended and Restated American Capacity Purchase Agreement is subject to termination prior to its expiration, subject to the Company’s right to cure, in various circumstances including:

•

If either American or the Company become insolvent, file for bankruptcy or fail to pay the debts as they become due, the non-defaulting party may terminate the agreement;

•

Failure by the Company or American to perform the covenants, conditions or provisions of the American Capacity Purchase Agreement, subject to 15 days' notice and cure rights;

•

If we are required by the FAA or the DOT to suspend operations and we have not resumed operations within three business days, except as a result of an emergency airworthiness directive from the FAA affecting all similarly equipped aircraft, American may terminate the agreement;

•

If our controllable flight completion factor falls below certain levels for a specified period of time, subject to our right to cure, or;

•

Upon the occurrence of a force majeure event (as defined in the Amended and Restated American Capacity Purchase Agreement) that lasts for a specified period of consecutive days and affects our ability to operate scheduled flights, including a future epidemic or pandemic;

•

If a labor dispute affects our ability to operate over a specified number of days or we operate in violation of any existing American collective bargaining agreement; or

•

Upon a change in our ownership or control without the written approval of American

United Capacity Purchase Agreement

As of March 31, 2021, we operated 60 E-175 and 16 E-175LL aircraft for United under the 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.

Under our United Capacity Purchase Agreement, United owns 42 of the 60 E-175 and all of the E-175LL 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 United owned E-175 aircraft.

On November 26, 2019, we amended and restated our United Capacity Purchase Agreement. The Amended and Restated United Purchase Agreement included the following amendments:

•

Addition of 20 new E-175 LL aircraft to be financed by the Company and operate them for a period of twelve (12) years from the aircraft acceptance and in-service date, expiring between November 2032 and June 2033.

•

Extended the term of the 42 E-175 aircraft leased from United for an additional five (5) years, which now expire between 2024 and 2028. Extended the term of the 18 E-175 aircraft that Company owns for an additional five (5) years, which now expires in 2028.

•

The Company agreed to lease our CRJ-700 aircraft to another United Express service provider for a term of nine (9) years. We ceased operating our CRJ-700 fleet in February 2021 in connection with the transfer of those aircraft into a lease agreement. The amendment also granted United a right to purchase the leased CRJ-700 aircraft at any point during the (9) year lease term for an amount representing the appraised value of the aircraft.

On November 4, 2020, we amended and restated our United Capacity Purchase Agreement. The amendments reflect the following:

•

Transferred the financing and ownership of the 20 new E-175 LL aircraft to United. The aircraft will be leased to the Company at nominal amounts to operate for a period of twelve (12) years from the aircraft acceptance and in-service date, expiring between November 2032 and June 2033.

•

As of March 31, 2021, 16 E-175LL have been delivered and the remaining 4 aircraft are expected to be delivered by the end of June 2021.

Our United Capacity Purchase Agreement is subject to following termination rights prior to its expiration.

•

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 E-175 aircraft from service, by giving us notice of 90 days or more.

•

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.

•

Commencing five (5) years after the actual in-service date, United has the right to remove the E-175LL 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.

Our United Capacity Purchase Agreement provides for temporary rate reductions for the period April 2020 to September 2020. The basis for the reduction is lower labor costs due to the grant received by the Company under the Payroll Support Program (PSP). The First Amendment also provides for further temporary rate reductions if the Payroll Support Program is extended.

DHL Flight Services

On December 20, 2019, the Company entered into a Flight Services Agreement with DHL. Under the terms of this agreement, Mesa operates two Boeing 737-400F aircraft to provide cargo air transportation services to DHL. In exchange for providing air services, the Company receives a fee per block hour with a minimum block hour guarantee. The Company is eligible for a monthly performance bonus or subject to a monthly penalty based on timeliness and completion performance. Ground support including fueling and airport fees are paid directly by DHL.

Under our Flight Services Agreement, DHL leases two Boeing 737-400F aircraft, and subleases them to us at nominal amounts. DHL reimburses us on a pass-through basis for all costs related to heavy maintenance including c-checks, off-wing engine maintenance and overhauls including LLPs, Landing Gear overhauls and LLPs, thrust reverser overhauls, and APU overhauls and LLPs. Certain items such as fuel, de-icing fluids, landing fees, aircraft ground handling fees, en-route navigation fees and custom fees are paid directly to suppliers by DHL or otherwise reimbursed if incurred by the Company.

The Flight Services Agreement expires five (5) years from the commencement date of the first aircraft placed into service. DHL has the option to extend the agreement with respect to one or more aircraft for a period of one year with 90 days’ advance written notice.

Our DHL Flight Services Agreement is subject to following termination rights prior to its expiration:

•

At any time under after the first anniversary of the commencement date of Aircraft with 90 day’s written notice;

•

Failure to comply with performance standards for three consecutive measurement periods;

•

DHL may terminate the agreement for a specific aircraft if it is subject to a total loss and the Company does not provide alternate services.

Summary of Significant Accounting Policies

6 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Basis of Presentation

The accompanying condensed 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. Reclassifications of certain immaterial prior period amounts have been made to conform to the current period presentation.

These condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements and notes thereto as of and for the year ended September 30, 2020 included in the Company's Annual Report on Form 10-K for the year ended September 30, 2020 on file with the U.S. Securities and Exchange Commission (the "SEC"). Information and footnote disclosures normally included in financial statements have been condensed or omitted in these condensed consolidated financial statements pursuant to the rules and regulations of the SEC and GAAP. These condensed consolidated financial statements reflect all adjustments that, in the opinion of management, are necessary to present fairly the results of operations for the interim periods presented.

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 its fiscal year following the fifth anniversary of the Company’s initial public offering (“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.

Segment Reporting

As of March 31, 2021, our chief operating decision maker was the Chief Executive Officer. While the Company operates under separate capacity purchase agreements, we do not manage our business based on any performance measure at the individual contract level. 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. Accordingly, we have a single operating and reportable segment.

Use of Estimates

The preparation of the Company's condensed 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 condensed consolidated financial statements. Actual results could differ from those estimates.

Contract revenue and Pass- through and other

The Company recognizes contract revenue when the service is provided under its capacity purchase agreements and flight services agreement. Under the capacity purchase agreements, our major partners generally pay for each departure, flight hour or block hour, and an amount per aircraft in service each month with additional incentives based on flight completion, on-time performance, and other operating metrics. The Company’s performance obligation is met as each flight is completed, and revenue is recognized and reflected in contract revenue.

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 including aircraft principal and interest debt service costs, aircraft depreciation and interest expense or aircraft lease expense costs while the aircraft is under contract. 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 $18.1 million and $52.4 million of lease revenue for the three months ended March 31, 2021 and 2020, respectively, and $67.6 million and $105.7 million during the six months ended March 31, 2021 and 2020, respectively. The Company has not separately stated aircraft rental income and aircraft rental expense in the consolidated statements of operations and comprehensive income because the use of the aircraft is not a separate activity of the total service provided under our capacity purchase agreements.

The Company recognizes pass-through revenue when the service is provided under its capacity purchase agreements and flight services agreement. Pass-through revenue represents reimbursements for certain direct expenses incurred including passenger liability and hull insurance, property taxes, other direct costs defined within the capacity purchase agreements, and major maintenance on aircraft leased at nominal rates. The Company’s performance obligation is met when each flight is completed or as the maintenance services are performed, and revenue is recognized and reflected in pass-through and other revenue.

The Company entered into lease agreements with GoJet Airlines LLC (“GoJet”) to lease 6 CRJ 700 aircraft as of March 2021. The lease agreements are accounted for as operating leases and have a term of nine-years beginning on the delivery date of each aircraft. The Company intends to lease our entire fleet of 20 CRJ 700 aircraft to GoJet with final aircraft deliveries expected by October 2021. Under the lease agreements, GoJet pays fixed monthly rent per aircraft and variable lease payments for supplemental rent based on monthly aircraft utilization at fixed rates. Supplemental rent payments are subject to reimbursement following GoJet’s completion of qualifying maintenance events defined in the agreements. Lease revenue for fixed monthly rent payments is recognized ratably within pass-through and other revenue. Lease revenue for supplemental rent is deferred and recognized within pass-through and other revenue when it is probable that amounts received will not be reimbursed for future qualifying maintenance events over the lease term.

The Company mitigates the residual asset risks through supplemental rent payments and by leasing aircraft and engine types that can be operated by the Company in the event of a default. Additionally, the operating leases have specified lease return condition requirements and the Company maintains inspection rights under the leases. As of March 31, 2021, the Company recognized $4.8 million of lease incentive assets and $4.2 million of related lease incentive obligations for reimbursement of certain aircraft maintenance costs defined within the lease agreements. Lease incentive assets will be recognized as a reduction to lease revenue over the lease term.

Lease revenue recognized and amounts deferred for supplemental rent payments were immaterial as of March 31, 2021. The following table summarizes future minimum rental income under operating leases related to leased aircraft that had remaining non-cancelable lease terms as of March 31, 2021 (In thousands):

Periods Ending March 31,	Total Payments
Remainder of 2021	$	3,276
2022		6,552
2023		6,552
2024		6,552
2025		6,552
Thereafter		28,962
Total	$	58,446

The Company records deferred revenue when cash payments are received or are due from our airline partners in advance of the Company’s performance, including amounts that are refundable. During the three months ended March 31, 2021, the Company deferred $4.9 million of revenue which was billed and paid by our partners.

The deferred revenue balance as of March 31, 2021 represents our aggregate remaining performance obligations that will be recognized as revenue over the period in which the performance obligations are satisfied, and is expected to be recognized as revenue as follows (In thousands):

Periods Ending March 31,	Total Maturities
Remainder of 2021	$	675
2022		9,097
2023		9,430
2024		9,169
2025		3,695
Thereafter		1,792
Total	$	33,858

Aircraft Leases

As discussed in Note 1, we lease, at nominal rates, certain aircraft from United and DHL under our United Capacity Purchase Agreement and DHL Flight Services Agreement, which are excluded from operating lease assets and liabilities as the lease contracts do not represent embedded leases under ASC 842. Other than nominal leases with our major partners, approximately 10% of our aircraft are leased from third parties. 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. 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. Additionally, any remaining ROU assets and lease liabilities would be written off.

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.

In March 2021, the Company purchased a leased CRJ 900 aircraft prior to the expiration of the lease term resulting in the lease termination expenses of $4.5 million. Termination expenses primarily related to the reversal of maintenance deposits on the aircraft that were no longer refundable from the lessor at termination of the lease.

Contract Liabilities

Contract liabilities consist of deferred credits for cost reimbursements from major airline partners related to aircraft modifications and employee training associated with capacity purchase agreements. 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 condensed consolidated balance sheets. The Company's total current and non-current deferred credit balances at March 31, 2021 and September 30, 2020 are $5.2 million and $8.5 million, respectively. The Company recognized $1.1 million and $0.9 million of the deferred credits within contract revenue during the three months ended March 31, 2021 and 2020, respectively, and $1.9 million and $2.0 million during the six months ended March 31, 2021 and 2020, respectively.

Maintenance Expense

The Company operates under an FAA approved continuous inspection and maintenance program. The cost of non-major scheduled inspections and repairs and routine maintenance costs for all aircraft and engines are charged to maintenance expense as incurred.

The Company accounts for heavy maintenance and major overhaul costs on our owned E-175 fleet under the deferral method whereby the cost of heavy maintenance and major overhaul is deferred and amortized until the earlier of the end of the useful life of the related asset or the next scheduled heavy maintenance event. Amortization of heavy maintenance and major overhaul costs charged to depreciation and amortization expense was immaterial for the three months and six months ended March 31, 2021 and 2020. At March 31, 2021 and September 30, 2020, the Company had deferred heavy maintenance balance, net of accumulated amortization, of $1.2 million and $0 million, respectively.

The Company accounts for heavy maintenance and major overhaul costs for all other fleets under the direct expense method where costs are expensed to maintenance expense as incurred, except for certain maintenance contracts where labor and materials price risks have been transferred to the service provider and require payment on a utilization basis, such as flight hours. Costs incurred for maintenance and repair for utilization maintenance contracts where labor and materials price risks have been transferred to the service provider are charged to maintenance expense based on contractual payment terms.

Engine overhaul expense totaled $6.9 million and $14.5 million for the three months ended March 31, 2021, and 2020, respectively, of which $2.2 million and $0.7 million, respectively, was pass-through expense. Engine overhaul expense totaled $21.3 million and $25.1 million for the six months ended March 31, 2021, and 2020, respectively, of which $11.8 million and $2.6 million, respectively, was pass-through expense. Airframe C-check expense totaled $14.1 million and $10.5 million for the three months ended March 31, 2021, and 2020, respectively, of which $5.6 million and $3.9 million, respectively, was pass-through expense. Airframe C-check expense totaled $24.2 million and $17.8 million for the six months ended March 31, 2021, and 2020, respectively, of which $12.7 million and $5.1 million, respectively, was pass-through expense.

Government Grant

In February 2021, the Company was granted $48.7 million in financial assistance by the Department of the Treasury under the Payroll Support Program Extension (“PSP2”) under the Consolidated Appropriations Act of 2021. In March 2021, we were notified that, based on funding availability, recipients that were currently in compliance with executed PSP agreements would receive an additional award amount. As a result, the company was granted an additional $7.3 million through the PSP2 for a total grant of $56.0 million. The additional $7.3 million was received in April 2021. PSP2 funding must be used exclusively for the continuation of payment of employee wages, salaries, and benefits and is conditioned on our agreement to refrain from conducting involuntary employee layoffs or furloughs from the date of the extension agreement through March 2021. Other conditions include prohibitions on share repurchases and dividends through March 2022 and certain limitations on executive compensation until October 2022. The Department of Transportation also has the authority until March 1, 2022 to require airlines that received payroll support program funds to maintain scheduled air service deemed necessary to any point served by the airline before March 1, 2020.

On April 15, 2021, the Company was notified by the U.S. Department of the Treasury we are eligible to receive funds under the third Payroll Support Program (PSP3), which was created under the American Recovery Plan Act of 2021 (ARP), enacted on March 11, 2021. PSP3 provides additional funding for passenger air carriers and contractors that received financial assistance under the Payroll Support Program Extension (PSP2). PSP3 funding must be used exclusively for the continuation of payment of employee wages, salaries, and benefits. Based on the share of funds we received from the first extension of the payroll support program, and the similar structures of both extensions, we estimate that we will receive approximately $52.2 million. However, the actual amounts received and the allocation could differ from our estimates. The Company received the first PSP3 installment of $26.1 million on April 23, 2021. These payments are conditioned on our agreement to refrain from conducting involuntary employee layoffs or furloughs through September 2021 or the date on which assistance provided under the agreement is exhausted, whichever is later. Other conditions would include prohibitions on share repurchases and dividends through September 2022 and certain limitations on executive compensation until April 2023.

During the three and six months ended March 31, 2021, the Company recognized $56.0 million and $67.3 million respectively, for the payroll support government funds. We deferred $11.3 million under PSP1 that was recognized during the three months ended December 31,2020. As of March 31,2021, there are no deferred payments.

Recent Accounting Pronouncements

6 Months Ended

Mar. 31, 2021

Accounting Changes And Error Corrections [Abstract]

Recent Accounting Pronouncements

3.	Recent Accounting Pronouncements

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”). This ASU provides optional expedients and exceptions for a limited period of time for accounting for contracts, hedging relationships, and other transactions affected by the London Interbank Offered Rate (LIBOR) or another reference rate expected to be

discontinued. Optional expedients can be applied from March 12, 2020 through December 31, 2022. We are currently evaluating the impact that the new guidance will have on our consolidated financial statements.

In June 2016, the FASB issued new guidance requiring all expected credit losses for financial instruments held at the reporting date to be measured based on historical experience, current conditions and reasonable supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial instruments measured at amortized cost and also applies to some off-balance sheet credit exposures. Our adoption of this guidance on a modified retrospective basis on October 1, 2020 did not have a material impact as credit losses have not been, and are not expected to be, significant based on historical collection trends, the financial condition of our airline partners and external market factors.

- Definition

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

+ References

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+ Details

Concentrations of Credit Risk

6 Months Ended

Mar. 31, 2021

Risks And Uncertainties [Abstract]

Concentrations of Credit Risk

4.	Concentrations of Credit Risk

Financial instruments that potentially expose the Company to a concentration of credit risk consist principally of cash and cash equivalents that are primarily held by financial institutions in the United States and accounts receivable. Amounts on deposit with a financial institution may at times exceed federally insured limits. The Company maintains its cash accounts with high credit quality financial institutions and, accordingly, minimal credit risk exists with respect to the financial institutions. As of March 31, 2021, the Company had $3.4 million in restricted cash. We have an agreement with a financial institution for letter of credit facility and to issue letters of credit for particular airport authorities, worker's compensation insurance, property and casualty insurance and other business needs as required in certain lease agreements. Pursuant to the term of this agreement, $3.4 million of outstanding letters of credit are required to be collateralized by amounts on deposit.

Significant customers are those which represent more than 10% of the Company’s total revenue or net accounts receivable balance at each respective balance sheet date. At March 31, 2021, the Company had capacity purchase agreements with American and United and a flight services agreement with DHL. Substantially all of the Company's condensed consolidated revenue for the six months ended March 31, 2021 and 2020 and accounts receivable at March 31, 2021 and September 30, 2020 was derived from these agreements. American accounted for approximately 45% and 51% of the Company's total revenue for the three months ended March 31, 2021 and 2020, respectively, and 46 % and 51% for the six months ended March 31, 2021 and 2020. United accounted for approximately 53% and 49% of the Company's revenue for the three months ended March 31, 2021 and 2020, respectively, and 52% and 49% for the six months ended March 31, 2021 and 2020. 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.

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 due based on historical collection trends, the financial condition of airline partners and external market factors and records a reserve for amounts estimated to be uncollectible. The allowance for doubtful accounts was $1.3 million and $0.8 million at March 31, 2021 and September 30, 2020, respectively. If the Company's ability to collect these receivables and the financial viability of its partners is materially different than estimated, the Company's estimate of the allowance could be materially impacted.

Intangible Assets

6 Months Ended

Mar. 31, 2021

Goodwill And Intangible Assets Disclosure [Abstract]

Intangible Assets

5.	Intangible Assets

Information about the intangible assets of the Company as of March 31, 2021 and September 30, 2020, is as follows (in thousands):

	March 31,			September 30,
	2021			2020
Customer relationship	$	43,800		$	43,800
Accumulated amortization		(36,388	)		(35,768	)
Net carrying value	$	7,412		$	8,032

Total amortization expense recognized was approximately $0.3 million and $0.4 million for the three months ended March 31, 2021 and 2020, respectively, and $0.6 million and $0.7 million for the six months ended March 31, 2021 and

2020 respectively. The Company expects to record amortization expense of $0.6 million for the remainder of 2021, and $1.0 million, $0.9 million, $0.8 million, $0.7 million for fiscal years 2022, 2023, 2024 and 2025, respectively.

As of March 31, 2021, the Company’s intangible assets remaining weighted average term is 14.6 years.

Balance Sheet Information

6 Months Ended

Mar. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Information

6.	Balance Sheet Information

Certain significant amounts included in the Company's condensed consolidated balance sheet as of March 31, 2021 and September 30, 2020, consisted of the following (in thousands):

	March 31,			September 30,
	2021			2020
Expendable parts and supplies, net:
Expendable parts and supplies	$	27,324		$	27,431
Less: obsolescence and other		(4,280	)		(4,460	)
	$	23,044		$	22,971

Prepaid expenses and other current assets:
Deferred offering and reimbursed costs	$	—		$	1,261
Other		8,956			14,806
	$	8,956		$	16,067
Property and equipment, net:
Aircraft and other flight equipment substantially pledged	$	1,603,377		$	1,596,174
Other equipment		5,189			5,147
Leasehold improvements		2,763			2,763
Vehicles		1,114			1,032
Building		699			699
Furniture and fixtures		303			302
Total property and equipment		1,613,445			1,606,117
Less: accumulated depreciation		(432,761	)		(393,702	)
	$	1,180,684		$	1,212,415
Other Assets:
Warrants	$	16,374		$	—
Other		4,273			—
	$	20,647		$	—
Other accrued expenses:
Accrued property taxes	$	5,996		$	11,354
Accrued interest		2,480			3,268
Accrued vacation		5,718			5,975
Other		14,416			24,881
	$	28,610		$	45,478

The Company records impairment charges on long-lived assets used in operations when events and circumstances indicate that the assets may be impaired, the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets, and the net book value of the assets exceeds their estimated fair value. The Company has assessed whether any impairment of its long-lived assets existed and has determined that no charges were deemed necessary under applicable accounting standards as of March 31, 2021. The Company’s assumptions about future conditions important to its assessment of potential impairment of its long-lived assets, including the impact of the COVID-19 pandemic to its business, are subject to uncertainty, and the Company will continue to monitor these conditions in future periods as new information becomes available, and will update its analyses accordingly.

Property and equipment, net:

Depreciation expense totaled approximately $20.4 million and $20.1 million for the three months ended March 31, 2021 and 2020, respectively, and $40.6 million and $40.3 million for the six months ended March 31, 2021 and 2020, respectively.

Other Assets

In connection with a negotiated forward purchase contract for electrically-powered vertical takeoff and landing aircraft (eVTOL aircraft) executed in February 2021, we obtained equity warrant assets giving us the right to acquire 1,171,649 shares of common stock in Archer Aviation, Inc. (Archer), a private, venture-backed company. Our investments in Archer do not have a readily determinable fair value, so we account for them using the measurement alternative under ASC 321 and measure the investments at cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments from the same issuer. We consider a range of factors when adjusting the fair value of these investments, including, but not limited to, the term and nature of the investment, local market conditions, values for comparable securities, current and projected operating performance, financing transactions subsequent to the acquisition of the investment or other features that indicate a discount to fair value is warranted. Any changes in fair value from the grant date fair value of the equity warrant assets will be recognized as increases or decreases on our balance sheet and as net gains or losses on equity warrant assets, in other (expense) income, net. We estimated the initial equity warrant asset value to be $16.4 million based on the Archer enterprise valuation disclosed within a February 10, 2021 S-4 filing with the SEC. There were no observable price changes or transactions as of March 31, 2021, and as such no adjustments to the recorded grant date fair value of the equity warrant assets was recorded.

The grant date value of the warrants, $16.4 million, was recognized as a vendor credit liability within other noncurrent liabilities. The liability related to the warrant assets will be settled in the future, as a reduction of the acquisition date value of the eVTOL aircraft contemplated in the related asset purchase agreement.

Fair Value Measurements

6 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

7.	Fair Value Measurements

Level 1

—

Quoted prices in active markets for identical assets or liabilities.

Level 2

—

Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Some of the Company’s marketable securities primarily utilize broker quotes in a non-active market for valuation of these securities.

Level 3

—

Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities, therefore requiring an entity to develop its own assumptions.

The carrying values reported in the condensed consolidated balance sheets for cash and cash equivalents, accounts receivable, and accounts payable approximate fair value because of the immediate or short-term maturity of these financial instruments.

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


	March 31, 2021				September 30, 2020
	Carrying		Fair		Carrying		Fair
	Value		Value		Value		Value
Long-term debt and financing leases, including current maturities⁽¹⁾	$	725.4	$	731.4	$	743.3	$	768.7

⁽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, Financing Leases and Other Borrowings

6 Months Ended

Mar. 31, 2021

Debt Disclosure [Abstract]

Long-Term Debt, Financing Leases and Other Borrowings

8.	Long-Term Debt, Financing Leases and Other Borrowings

Long-term debt as of March 31, 2021 and September 30, 2020, consisted of the following (in thousands):

	March 31,			September 30,
	2021			2020
Notes payable to financial institution, collateralized by the underlying
aircraft, due 2022⁽¹⁾⁽²⁾	$	—		$	41,472
Notes payable to financial institution, collateralized by the underlying
aircraft, due 2024⁽³⁾		—			55,674
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2027⁽⁴⁾		106,092			105,887
Notes payable to secured parties, collateralized by the underlying
aircraft, due 2028⁽⁵⁾		162,247			172,137
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2028⁽⁶⁾		130,505			138,114
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2022⁽⁷⁾		—			47,319
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2022⁽⁸⁾		—			29,682
Notes payable to financial institution due 2020⁽¹⁰⁾		1,523			1,523
Notes payable to financial institution, collateralized by the underlying
equipment, due 2020⁽¹¹⁾		—			4,182
Other obligations due to financial institution, collateralized by the underlying
equipment, due 2023⁽¹²⁾		5,663			6,864
Notes payable to financial institution, collateralized by the underlying
equipment, due 2024⁽¹³⁾		54,573			63,341
Notes payable to financial institution, collateralized by the underlying
aircraft, due 2023⁽¹⁴⁾		39,375			48,125
Notes payable to financial institution due 2023 ⁽¹⁵⁾		5,000			6,000
Revolving Credit Facility ⁽¹⁶⁾		22,930			22,930
Notes payable to financial institution due 2025 ⁽¹⁷⁾		197,525			—
Gross long-term debt, including current maturities		725,433			743,250
Less unamortized debt issuance costs		(10,598	)		—
Less Notes payable warrants		(10,797	)		(11,526	)
Net long-term debt, including current maturities		704,038			731,724
Less current portion		(103,980	)		(189,268	)
Net long-term debt	$	600,058		$	542,456

⁽¹⁾	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% and requires monthly principal and interest payments. The loan was paid in full during quarter ended December 31, 2020.

⁽²⁾

In fiscal 2014, the Company financed ten CRJ-900 aircraft for $88.4 million. The debt bears interest at the monthly LIBOR plus 1.95% and requires monthly principal and interest payments. In fiscal 2018, the Company repaid $40.0 million related to four CRJ-900 aircraft. During quarter ended December 31, 2020, the company paid the remaining balance in full.

⁽³⁾	In fiscal 2014, the Company financed eight CRJ-900 aircraft with $114.5 million in debt. The debt bears interest at 5.00% and requires monthly principal and interest payments. The loan was paid in full during quarter ended December 31, 2020.

⁽⁴⁾

In fiscal 2015, the Company financed seven CRJ-900 aircraft with $170.2 million in debt. The senior notes payable of $151.0 million bear interest at monthly LIBOR plus 2.71% and require monthly principal and interest payments. The subordinated notes payable is 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.

⁽⁵⁾	In fiscal 2016, the Company financed ten E-175 aircraft with $246.0 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.

⁽⁶⁾

In fiscal 2016, the Company financed eight E-175 aircraft with $195.3 million in debt. The senior notes payable of $172.0 million bear interest at the three-month LIBOR plus a spread ranging from 2.20% to 2.32% and require quarterly principal and interest payments. The subordinated notes payable bear interest at 4.50% and require quarterly principal and interest payments.

⁽⁷⁾

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% and require quarterly principal and interest payments. The subordinated notes payable of $29.8 million bear interest at three month LIBOR plus 7.50% and require quarterly principal and interest payments. The loan was paid in full during quarter ended December 31, 2020.

⁽⁸⁾

InDecember 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% and require quarterly principal and interest payments. The subordinated notes payable bear interest at the three-month LIBOR plus 4.50% and require quarterly principal and interest payments. The loan was paid in full during quarter ended December 31, 2020.

⁽¹⁰⁾	In fiscal 2015 and 2016, 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% and requires quarterly principal and interest payments.

⁽¹¹⁾

In fiscal 2016-2019, the Company financed certain flight equipment maintenance costs with $26.1 million in debt. The debt bears interest at the three-month LIBOR plus a spread ranging from 2.93% to 3.21%and requires quarterly principal and interest payments. The debt is subject to a fixed charge ratio covenant. The loan was paid in full during quarter ended December 31, 2020.

⁽¹²⁾	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.

⁽¹³⁾	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% and requires monthly principal and interest payments.

⁽¹⁴⁾

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 5.00% and requires monthly principal and interest payments. The interest rate reduced from 5.25% to 5.00% in 1^st quarter, 2020 due to United Airlines extension of CRJ-700.

⁽¹⁵⁾

On September 27,2019, the Company financed certain flight equipment for $8.0 million. The debt bears interest at the monthly LIBOR plus 5.00% and requires monthly principal and interest payments. The interest rate reduced from 5.25% to 5.00% in 1^st quarter, 2020 due to United Airlines extension of CRJ-700.

⁽¹⁶⁾

On September 25, 2019, the Company extended the term on their $35.0 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%. During quarter ended June 30, 2020, $23.0 million was drawn to cover operational needs.

⁽¹⁷⁾

^{On October 30, 2020, the Company entered into a loan and guarantee agreement with United States Department of Treasury for a secured loan facility of up to $200.0 million that matures on October 30, 2025. On October 30, 2020, the Company borrowed $43.0 million and on November 13, 2020, the Company borrowed an additional $152.0 million. These amounts bear interest at the three-month LIBOR plus 3.50% which was paid-in-kind and capitalized into the balance of the loans for the first interest payment date on December 15, 2020. No further borrowings are available under the Loan and Guarantee Agreement.}

Principal maturities of long-term debt as of March 31, 2021, and for each of the next five years are as follows (in thousands):

March 31, 2021	Total Principal
Remainder of 2021	$	59,013
2022		113,682
2023		89,462
2024		61,209
2025		56,526
Thereafter		345,541
	$	725,433

The net book value of collateralized aircraft and equipment as of March 31, 2021 was $1,060.0 million.

Enhanced Equipment Trust Certificate ("EETC")

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 March 31, 2021 Mesa has $162.2 million of equipment notes outstanding issued under the EETC financing included in long-term debt on the condensed 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.

CIT Revolving Credit Facility

On September 25, 2019, the Company extended the term on their $35.0 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%. As of March 31, 2021, $22.9 million has been drawn on the revolver.

Future borrowings, if any, under this facility are subject to, among other things, the Company having sufficient unencumbered assets to meet the borrowing base requirements under the facility.

Loan agreement with United States Department of Treasury

On October 30, 2020, the Company entered into a Loan and Guarantee Agreement with United States Department of Treasury (the “U.S. Treasury”) for a secured loan facility of up to $200.0 million that matures in October 2025 (“the Treasury Loan Agreement”). On October 30, 2020, the Company borrowed $43.0 million (“the $43M Treasury Loan”) and on November 13, 2020, the Company borrowed an additional $152.0 million (“the $152M Treasury Loan”), collectively referred to as the “Treasury Term Loan Facility”. No further borrowings are available under the Treasury Loan Agreement. The Company also issued warrants to purchase shares of common stock to the U.S. Treasury.

The Loan and Guarantee Agreement bear interest at a variable rate equal to (a)(i) the LIBOR rate divided by (ii) one minus the Eurodollar Reserve Percentage plus (b) 3.50%. Accrued interest on the loans will be payable in arrears on the first business day following the 14^th day of each March, June, September and December, beginning with December 15, 2021.

All principal amounts outstanding under the Loan and Guarantee Agreement are due and payable in a single installment on October 30, 2025 (the “Maturity Date”). Interest will be paid by increasing the principal amount of the loan by the amount of such interest due on an interest payment date for the first 12 months. Mesa's obligations under the Treasury Loan Agreement are secured by certain aircraft, aircraft engines, accounts receivable, ground service equipment and tooling (collectively, the “Collateral”). The obligations under the Loan Agreement are guaranteed by the Company and Mesa Air Group Inventory Management. The proceeds may be used for general corporate purposes and operating expenses, to the extent permitted by the CARES Act. Voluntary prepayments of loans under the Loan Agreement may be made, in whole or in part, by Mesa Airlines, without premium or penalty, at any time and from time to time. Amounts prepaid may not be reborrowed. Mandatory prepayments of loans under the Loan Agreement are required, without premium or penalty, to the extent necessary to comply with the covenants discussed below, certain dispositions of the Collateral, certain debt issuances secured by liens on the Collateral and certain insurance payments related to the Collateral. In addition, if a “change of control” (as defined in the Loan Agreement) occurs with respect to Mesa Airlines, Mesa Airlines will be required to repay the loans outstanding under the Loan Agreement.

The Loan Agreement requires the Company, under certain circumstances, including within ten (10) business days prior to the last business day of March and September of each year, beginning March 2021, to appraise the value of the Collateral and recalculate the collateral coverage ratio. If the calculated collateral coverage ratio is less than 1.6 to 1.0, Mesa Airlines will be required either to provide additional Collateral (which may include cash collateral) to secure its obligations under the Loan Agreement or repay the term loans under the Loan Agreement, in such amounts that the recalculated collateral coverage ratio, after giving effect to any such additional Collateral or repayment, is at least 1.6 to 1.0.

The Loan Agreement contains two financial covenants, a minimum collateral coverage ratio and a minimum liquidity level. The Loan Agreement also contains customary negative and affirmative covenants for credit facilities of this type, including, among others: (a) limitations on dividends and distributions; (b) limitations on the creation of certain liens; (c) restrictions on certain dispositions, investments and acquisitions; (d) limitations on transactions with affiliates; (e) restrictions on fundamental changes to the business, and (f) restrictions on lobbying activities. Additionally, the Company is required to comply with the relevant provisions of the CARES Act, including limits on employment level reductions after September 30, 2020, restrictions on dividends and stock buybacks, limitations on executive compensation, and requirements to maintain certain levels of scheduled service.

In connection with the Loan and Guarantee Agreement and as partial compensation to Treasury for the provision of financial assistance under the Loan and Guarantee Agreement, the Company issued to Treasury warrants to purchase an aggregate of 4,899,497 shares of the Company’s common stock at an exercise price of $3.98 per share, which was the closing price of the Common Stock on The Nasdaq Stock Market on April 9, 2020. The exercise price and number of shares of common stock issuable under the Warrants are subject to adjustment as a result of anti-dilution provisions contained in the Warrants for certain stock issuances, dividends, and other corporate actions. The warrants expire on the fifth anniversary of the date of issuance and are exercisable either through net share settlement or net cash settlement, at the Company’s option. For accounting purposes, the fair value for the Treasury Loan Warrant Shares is estimated using a Black-Scholes option pricing model and recorded in stockholders' equity with an offsetting debt discount to the Treasury Term Loan Facility in the condensed consolidated balance sheet.

The Company incurred $3.1 million in debt issuance costs relating to the Loan and Guarantee Agreement. In accordance with the applicable guidance, Mesa allocated the debt issuance costs between the Treasury Loan and related warrants. At funding on October 30, 2020, the $43M Treasury Loan was recorded net of $0.7 million in capitalized debt issuance costs. At funding on November 13, 2020, the $152M Treasury Loan was recorded net of $2.3 million in capitalized debt issuance costs. The remaining $0.1 million in debt issuance costs was allocated to the warrants as a reduction to the warrant value within additional paid-in capital. Debt issuance costs allocated to the debt are amortized into interest expense using the effective interest method over the term of the related loan.

Debt Repayment

Prior to the November 13, 2020 funding of the $152M Treasury Loan, the Company repaid $167.7 million in existing aircraft debt covering 44 aircraft, including indebtedness under its (a) Senior Loan Agreements, dated June 27, 2018, (b) Junior Loan Agreements, also dated June 27, 2018, (c) Credit Agreements, dated January 31, 2007, April 16, 2014, and May 23, 2014, (d) Senior Loan Agreements, dated December 27, 2017, and (e) Junior Loan Agreements, also dated December 27, 2017 (collectively, “the EDC Loans”). The Company made payments totaling $164.1 million to repay the EDC Loans, consisting of principal of $167.7 million, and a $3.6 million discount on the balance owed. Additionally, in connection with the repayment, $2.5 million of unamortized original issue discount and deferred financing costs were recorded as a loss on debt extinguishment, resulting in a net gain on extinguishment of $1.0 million recorded within other income.

As of March 31, 2021, the Company is in compliance will all debt covenants.

Earnings Per Share and Equity

6 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Earnings Per Share and Equity

9.	Earnings Per Share and Equity

Calculations of net income per common share attributable to Mesa Air Group were as follows (in thousands, except per share data):

	Three Months Ended March 31,				Six Months Ended March 31,
	2021		2020		2021		2020
Net income attributable to Mesa Air Group	$	5,689	$	1,885	$	19,807	$	12,670
Basic weighted average common shares outstanding		35,628		35,141		35,579		35,082
Add: Incremental shares for:
Dilutive share adjustment - UST Warrant		3,038		—		2,183		138
Dilutive share adjustment - Restricted Shares		766		124		620		—
Diluted weighted average common shares outstanding		39,432		35,265		38,382		35,220
Net income per common share attributable to Mesa Air Group:
Basic	$	0.16	$	0.05	$	0.56	$	0.36
Diluted	$	0.14	$	0.05	$	0.52	$	0.36

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 three and six months ended March 31, 2021 and 2020.

Common Stock

6 Months Ended

Mar. 31, 2021

Stockholders Equity Note [Abstract]

Common Stock

10.	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. Persons who were not U.S. citizens held certain of these outstanding warrants. 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). All of these warrants were converted to common shares as of March 31, 2020 and these warrants were not related to any of the warrants the Company issued pursuant to the terms of a Treasury Warrant Agreement under the Loan and Guarantee Agreement entered on October 30, 2020.

In July 2018, the Company's Board of Directors and Compensation Committee approved the issuance of shares of restricted common stock under its 2018 Equity Incentive Plan (the "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 April 9, 2019, and pursuant to Section 4.4 of the 2018 Plan in connection with the 2.5-for-1 stock split effected on August 8, 2018, 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.

On October 30, 2020, the Company entered into the Loan and Guarantee Agreement with the United States Department of the Treasury (the “Treasury”) and the Bank of New York Mellon, as Administrative and Collateral Agent, under the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”).

In connection with the Loan and Guarantee Agreement and as partial compensation to the Treasury for the provision of financial assistance under the Loan and Guarantee Agreement, the Company issued warrants to the Treasury to purchase shares of the Company’s common stock, no par value, at an exercise price of $3.98 per share (the “Exercise Price”), which was the closing price of the Common Stock on The Nasdaq Stock Market on April 9, 2020. The Warrants were issued pursuant to the terms of a Treasury Warrant Agreement entered into by the Company and the Treasury. The exercise price and number of Warrant Shares issuable under the Warrants are subject to adjustment as a result of anti-dilution provisions contained in the Warrants for certain stock issuances, dividends, and other corporate actions. The warrants expire on the fifth anniversary of the date of issuance and are exercisable either through net share settlement or net cash settlement, at the Company’s option. The warrants will be accounted for within equity at a grant date fair value determined under the Black Scholes Option Pricing Model. As of March 31, 2021, 4,899,497 warrants were issued and outstanding.

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

Income Taxes

6 Months Ended

Mar. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

11.	Income Taxes

The Company’s effective tax rate (ETR) from continuing operations was 24.9% and 25.3% for the three months and six months ended March 31, 2021, respectively and 40.9% and 27.6% for the three months and six months ended March 31,2020, respectively. The Company's ETR during the three months and six months ended March 31, 2021 was different from the prior year tax rates as a result of vesting of stock compensation where the tax deduction state taxes differed from the book expense, changes in the valuation allowance against state net operating losses, and changes in state statutory rates.

The Company's ETR during the six months ended March 31, 2020 was different than the statutory rate of 21% as a result of the vesting and exercise of stock compensation, state taxes, and changes in valuation allowance against state net operating losses, as well as differences between the book and tax deductions associated with meals, entertainment, employer provided parking, and compensation of officers.

As of September 30, 2020, the Company had aggregate federal and state net operating loss carryovers of approximately $512.4 million and $223.9 million, respectively, which expire in fiscal years 2027-2038 and 2021-2040, respectively. Approximately $0.7 million of state net operating loss carryforwards are expected to expire in the current fiscal year.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Share-Based Compensation and Stock Repurchases

6 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation and Stock Repurchases

12.	Share-Based Compensation and Stock Repurchases

Restricted Stock

The restricted share activity for the six months ended March 31, 2021 were summarized as follows:

				Weighted-
				Average
	Number			Grant Date
	of Shares			Fair Value
Restricted shares unvested at September 30, 2020		1,195,548		$	5.47
Granted		121,688			8.58
Vested		(132,109	)		8.75
Forfeited		(17,500	)		4.90
Restricted shares unvested at March 31, 2021		1,167,627		$	5.44

As of March 31, 2021, there was $4.4 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 2.3 years.

Compensation cost for share-based awards are recognized on a straight-line basis over the vesting period. Share-based compensation expense for the three months ended March 31, 2021 and 2020 was $0.8 million and $1.2 million, respectively, and for the six months ended March 31, 2021 and 2020 was $1.7 million and $2.5 million, respectively.

The Company repurchased 175,925 shares of its common stock for $0.2 million to cover the income tax obligation on vested employee equity awards and warrant conversions during the six months ended March 31, 2021.

The Company has granted restricted stock units (“RSUs”) as part of its long-term incentive compensation to employees and non-employee members of the Board of Directors. 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 RSUs are not deemed issued or outstanding upon grant, and do not carry any voting rights.

Employee Stock Purchase Plan

6 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Employee Stock Purchase Plan

13.	Employee Stock Purchase Plan

2019 ESPP

The Mesa Air Group, Inc. 2019 Employee Stock Purchase Plan (the "2019 ESPP") is a nonqualified plan that provides eligible employees of Mesa Air Group, Inc. with an opportunity to purchase Mesa Air Group, Inc. ordinary shares through payroll deductions. Under the 2019 ESPP, eligible employees may purchase Mesa Air Group, Inc. ordinary shares through the Employee Stock Purchase Plan. Under the 2019 ESPP, eligible employees may elect to contribute 1% to 15% of their eligible compensation during each semi-annual offering period to purchase Mesa Air Group, Inc. ordinary shares at a 10% discount.

A maximum of 500,000 Mesa Air Group, Inc. ordinary shares may be issued under the 2019 ESPP. As of March 31, 2021, eligible employees purchased and the Company issued 157,714 Mesa Air Group, Inc. ordinary shares under the 2019 ESPP.

Commitments and Contingencies

6 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

14.	Commitments and Contingencies

Leases

As of March 31, 2021, the Company leased 17 aircraft, airport facilities, office space, and other property and equipment under non-cancelable operating leases. 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. The Company expects that, in the normal course of business, such operating leases that expire will be renewed or replaced by other leases, or the property may be purchased rather than leased.

It is common for us, as the lessee, to agree to indemnify the lessor and the lessor's related parties for tort, environmental and other liabilities that arise out of or relate to our use or occupancy of the leased airport facility and office space premises. This type of indemnity typically makes us responsible to indemnified parties for liabilities arising out of the conduct of, among others, contractors, licensees and invitees at, or in connection with, the use or occupancy of the leased premises. This indemnity often extends to related liabilities arising from the negligence of the indemnified parties but usually excludes any liabilities caused by either their sole or gross negligence or their willful misconduct.

Our aircraft and other equipment lease and financing agreements typically contain provisions requiring us, as the lessee or obligor, to indemnify the other parties to those agreements, including certain of those parties' related persons, against virtually any liabilities that might arise from the use or operation of the aircraft or other equipment.

We believe that our insurance would cover most of our exposure to liabilities and related indemnities associated with the commercial real estate leases and aircraft and other equipment lease and financing agreements described above. While our insurance does not typically cover environmental liabilities, we have insurance policies in place as required by applicable environmental laws. We cannot reasonably estimate our potential future payments under the indemnities and related provisions described above because we cannot predict (1) when and under what circumstances these provisions may be triggered and (2) the amount that would be payable if the provisions were triggered because the amounts would be based on facts and circumstances existing at such time.

Aggregate rental expense under all operating aircraft, equipment and facility leases totaled approximately $13.9 million and $18.6 million for the three months ended March 31, 2021 and 2020, respectively, and $27.7 million and $35.4 million for the six months ended March 31, 2021 and 2020, respectively.

As of March 31, 2021, the Company’s operating leases have a remaining weighted average lease terms of 3.1 years and our operating lease liabilities were measured using a weighted average discount rate of 4.2%.

Engine Purchase Commitments

On February 26, 2021, the Company and General Electric Company (“GE”), acting through its GE-Aviation business unit, entered into an Amended and Restated Letter Agreement No. 13-3. The Company agreed to purchase and take delivery of 10 new CF34-8C5 or CF34-8E5 engines with delivery dates starting from July 1, 2021 through November 1^,2022. During the quarter ended March 31, 2021, a $7.0 million non-refundable purchase deposit was made for the first five engines to be delivered in calendar 2021. The Company has options to purchase an additional (10) ten similar engines beyond 2022. The total purchase commitment related to these 10 engines is approximately $50.0 million.

If the Company fails to accept delivery of the spare engines when duly tendered, the Company may be assessed a minimum cancellation charge based on the engine price determined as of the date of scheduled engine delivery to the Company.

Other

We have certain contracts for goods and services that require us to pay a penalty, acquire inventory specific to us or purchase contract-specific equipment, as defined by each respective contract, if we terminate the contract without cause prior to its expiration date. Because these obligations are contingent on our termination of the contract without cause prior to its expiration date, no obligation would exist unless such a termination occurs.

Litigation

The Company is subject to two putative class action lawsuits alleging federal securities law violations in connection with our IPO, one in the Superior Court of the State of Arizona and one in U.S. District Court of Arizona. These purported class actions were filed in March and April 2020 against the Company, certain current and former officers and directors, and certain underwriters of the Company’s IPO. The state and federal lawsuits each make the same or similar allegations of violations of the Securities Act of 1933, as amended, for allegedly making materially false and misleading statements in, or omitting material information from, our IPO registration statement. The plaintiffs seek unspecified monetary damages and other relief. In addition, we are subject to certain legal actions which we consider routine to our business activities. As of March 31, 2021, our management believed, after consultation with legal counsel, that the ultimate outcome of the two putative class action lawsuits and such other routine legal matters are not likely to have a material adverse effect on our financial position, liquidity or results of operations.

Subsequent Events

6 Months Ended

Mar. 31, 2021

Subsequent Events [Abstract]

Subsequent Events

15.	Subsequent Events

On April 15, 2021, the Company was notified by the U.S. Department of the Treasury we are eligible to receive funds under the third Payroll Support Program (PSP3) as described in Note 2.

On April 9, 2021, the Company entered into Amendment No. 2 (“Amendment No. 2”) to the Amended and Restated American Capacity Purchase Agreement as described in Note 1.

On April 19, 2021, the Company entered into Amendment No. 3 (“Amendment No. 3”) to the Amended and Restated American Capacity Purchase Agreement as described in Note 1.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Basis of Presentation

Segment Reporting

Use of Estimates

Contract revenue and Pass- through and other

Periods Ending March 31,	Total Payments
Remainder of 2021	$	3,276
2022		6,552
2023		6,552
2024		6,552
2025		6,552
Thereafter		28,962
Total	$	58,446

Periods Ending March 31,	Total Maturities
Remainder of 2021	$	675
2022		9,097
2023		9,430
2024		9,169
2025		3,695
Thereafter		1,792
Total	$	33,858

Aircraft Leases

Disclosure of accounting policy for segment reporting.

+ References + Details

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Schedule of Future Minimum Rental Income under Non-cancelable Operating Leases

The following table summarizes future minimum rental income under operating leases related to leased aircraft that had remaining non-cancelable lease terms as of March 31, 2021 (In thousands):

Periods Ending March 31,	Total Payments
Remainder of 2021	$	3,276
2022		6,552
2023		6,552
2024		6,552
2025		6,552
Thereafter		28,962
Total	$	58,446

Schedule of Deferred Revenue Remaining Performance Obligations

Periods Ending March 31,	Total Maturities
Remainder of 2021	$	675
2022		9,097
2023		9,430
2024		9,169
2025		3,695
Thereafter		1,792
Total	$	33,858

Intangible Assets (Tables)

6 Months Ended

Mar. 31, 2021

Goodwill And Intangible Assets Disclosure [Abstract]

Information About Intangible Assets

Information about the intangible assets of the Company as of March 31, 2021 and September 30, 2020, is as follows (in thousands):

	March 31,			September 30,
	2021			2020
Customer relationship	$	43,800		$	43,800
Accumulated amortization		(36,388	)		(35,768	)
Net carrying value	$	7,412		$	8,032

Balance Sheet Information (Tables)

6 Months Ended

Mar. 31, 2021

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 condensed consolidated balance sheet as of March 31, 2021 and September 30, 2020, consisted of the following (in thousands):

	March 31,			September 30,
	2021			2020
Expendable parts and supplies, net:
Expendable parts and supplies	$	27,324		$	27,431
Less: obsolescence and other		(4,280	)		(4,460	)
	$	23,044		$	22,971

Prepaid expenses and other current assets:
Deferred offering and reimbursed costs	$	—		$	1,261
Other		8,956			14,806
	$	8,956		$	16,067
Property and equipment, net:
Aircraft and other flight equipment substantially pledged	$	1,603,377		$	1,596,174
Other equipment		5,189			5,147
Leasehold improvements		2,763			2,763
Vehicles		1,114			1,032
Building		699			699
Furniture and fixtures		303			302
Total property and equipment		1,613,445			1,606,117
Less: accumulated depreciation		(432,761	)		(393,702	)
	$	1,180,684		$	1,212,415
Other Assets:
Warrants	$	16,374		$	—
Other		4,273			—
	$	20,647		$	—
Other accrued expenses:
Accrued property taxes	$	5,996		$	11,354
Accrued interest		2,480			3,268
Accrued vacation		5,718			5,975
Other		14,416			24,881
	$	28,610		$	45,478

Fair Value Measurements (Tables)

6 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

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

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


	March 31, 2021				September 30, 2020
	Carrying		Fair		Carrying		Fair
	Value		Value		Value		Value
Long-term debt and financing leases, including current maturities⁽¹⁾	$	725.4	$	731.4	$	743.3	$	768.7

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

Long-Term Debt, Financing Leases and Other Borrowings (Tables)

6 Months Ended

Mar. 31, 2021

Debt Disclosure [Abstract]

Schedule of Long-term Debt

Long-term debt as of March 31, 2021 and September 30, 2020, consisted of the following (in thousands):

	March 31,			September 30,
	2021			2020
Notes payable to financial institution, collateralized by the underlying
aircraft, due 2022⁽¹⁾⁽²⁾	$	—		$	41,472
Notes payable to financial institution, collateralized by the underlying
aircraft, due 2024⁽³⁾		—			55,674
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2027⁽⁴⁾		106,092			105,887
Notes payable to secured parties, collateralized by the underlying
aircraft, due 2028⁽⁵⁾		162,247			172,137
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2028⁽⁶⁾		130,505			138,114
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2022⁽⁷⁾		—			47,319
Senior and subordinated notes payable to secured parties, collateralized
by the underlying aircraft, due 2022⁽⁸⁾		—			29,682
Notes payable to financial institution due 2020⁽¹⁰⁾		1,523			1,523
Notes payable to financial institution, collateralized by the underlying
equipment, due 2020⁽¹¹⁾		—			4,182
Other obligations due to financial institution, collateralized by the underlying
equipment, due 2023⁽¹²⁾		5,663			6,864
Notes payable to financial institution, collateralized by the underlying
equipment, due 2024⁽¹³⁾		54,573			63,341
Notes payable to financial institution, collateralized by the underlying
aircraft, due 2023⁽¹⁴⁾		39,375			48,125
Notes payable to financial institution due 2023 ⁽¹⁵⁾		5,000			6,000
Revolving Credit Facility ⁽¹⁶⁾		22,930			22,930
Notes payable to financial institution due 2025 ⁽¹⁷⁾		197,525			—
Gross long-term debt, including current maturities		725,433			743,250
Less unamortized debt issuance costs		(10,598	)		—
Less Notes payable warrants		(10,797	)		(11,526	)
Net long-term debt, including current maturities		704,038			731,724
Less current portion		(103,980	)		(189,268	)
Net long-term debt	$	600,058		$	542,456

⁽¹⁾	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% and requires monthly principal and interest payments. The loan was paid in full during quarter ended December 31, 2020.

⁽²⁾

⁽³⁾	In fiscal 2014, the Company financed eight CRJ-900 aircraft with $114.5 million in debt. The debt bears interest at 5.00% and requires monthly principal and interest payments. The loan was paid in full during quarter ended December 31, 2020.

⁽⁴⁾

⁽⁵⁾	In fiscal 2016, the Company financed ten E-175 aircraft with $246.0 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.

⁽⁶⁾

⁽⁷⁾

⁽⁸⁾

⁽¹⁰⁾	In fiscal 2015 and 2016, 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% and requires quarterly principal and interest payments.

⁽¹¹⁾

⁽¹²⁾	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.

⁽¹³⁾	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% and requires monthly principal and interest payments.

⁽¹⁴⁾

⁽¹⁵⁾

⁽¹⁶⁾

⁽¹⁷⁾

Schedule of Principal Maturities of Long-term Debt

Principal maturities of long-term debt as of March 31, 2021, and for each of the next five years are as follows (in thousands):

March 31, 2021	Total Principal
Remainder of 2021	$	59,013
2022		113,682
2023		89,462
2024		61,209
2025		56,526
Thereafter		345,541
	$	725,433

Earnings Per Share and Equity (Tables)

6 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Calculations of Net Income Per Common Share

Calculations of net income per common share attributable to Mesa Air Group were as follows (in thousands, except per share data):

	Three Months Ended March 31,				Six Months Ended March 31,
	2021		2020		2021		2020
Net income attributable to Mesa Air Group	$	5,689	$	1,885	$	19,807	$	12,670
Basic weighted average common shares outstanding		35,628		35,141		35,579		35,082
Add: Incremental shares for:
Dilutive share adjustment - UST Warrant		3,038		—		2,183		138
Dilutive share adjustment - Restricted Shares		766		124		620		—
Diluted weighted average common shares outstanding		39,432		35,265		38,382		35,220
Net income per common share attributable to Mesa Air Group:
Basic	$	0.16	$	0.05	$	0.56	$	0.36
Diluted	$	0.14	$	0.05	$	0.52	$	0.36

Share-Based Compensation and Stock Repurchases (Tables)

6 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Restricted Share Activity

The restricted share activity for the six months ended March 31, 2021 were summarized as follows:

				Weighted-
				Average
	Number			Grant Date
	of Shares			Fair Value
Restricted shares unvested at September 30, 2020		1,195,548		$	5.47
Granted		121,688			8.58
Vested		(132,109	)		8.75
Forfeited		(17,500	)		4.90
Restricted shares unvested at March 31, 2021		1,167,627		$	5.44

Organization and Operations - Additional Information (Detail)							1 Months Ended	2 Months Ended			6 Months Ended
	Mar. 31, 2021 Daily_Departure State Air-craft	Mar. 04, 2021 Air-craft	Nov. 19, 2020 Air-craft	Nov. 04, 2020 Air-craft	Dec. 20, 2019 Air-craft	Nov. 26, 2019 Air-craft Airfleet	Jun. 02, 2021 Air-craft	Aug. 17, 2021 Air-craft	May 05, 2021 Air-craft	Mar. 03, 2021 Air-craft	Mar. 31, 2021 Daily_Departure State Air-craft City Employee
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of states in which entity operates \| State	38										38
Number of aircrafts operated											163
Number of cities in which entity operates \| City											112
Number of daily departures \| Daily_Departure	440										440
Number of employees \| Employee											3,111
American Capacity Purchase Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Amendment Term			5 years
Maximum number of aircraft withdraw in twenty twenty one			10
Maximum number of aircraft withdraw in twenty twenty two			5
Maximum number of aircraft withdraw in twenty twenty three			5
Number of aircraft removed due to failure to meet certain performance objectives			20
Number of aircraft removed due to failure to meet certain performance objectives thereafter			20
American Capacity Purchase Agreement [Member] \| CRJ-900 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated			40								45
Amended and Restated American Capacity Purchase Agreement [Member] \| CRJ-900 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts expected to operate		5								3
American Capacity Purchase Agreement (Amendment No. 2) [Member] \| CRJ-900 Aircraft [Member] \| Scenario Forecast [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts expected to operate							3	5
American Capacity Purchase Agreement (Amendment No. 2) [Member] \| CRJ-900 Aircraft [Member] \| Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts expected to operate									5
United Capacity Purchase Agreement [Member] \| E-175 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated											60
United Capacity Purchase Agreement [Member] \| E-175 Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated											42
Aircraft lease extension period						5 years
Number of aircraft leased						42
Lease expiration year						2028
Number of aircrafts owned \| Airfleet						18
Notice period for termination of 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 E-175 aircraft from service, by giving us notice of 90 days or more
United Capacity Purchase Agreement [Member] \| E-175 Aircraft [Member] \| United [Member] \| Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Lease expiration year						2024
United Capacity Purchase Agreement [Member] \| E-175 Aircraft [Member] \| United [Member] \| Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Lease expiration year						2028
United Capacity Purchase Agreement [Member] \| E175LL Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated											16
Number of additional aircrafts						20
Number of years in operation						12 years
Air crafts expiring month and year description											expiring between November 2032 and June 2033
Number of aircraft leased				20
Aircraft lease term				12 years
Number of aircraft delivered	16
Number of aircraft expected to delivered	4
United Capacity Purchase Agreement [Member] \| E175LL Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Notice period for termination of agreement											Commencing five (5) years after the actual in-service date, United has the right to remove the E-175LL 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
United Capacity Purchase Agreement [Member] \| CRJ-700 Aircraft [Member] \| United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Aircraft lease term						9 years
DHL Flight Services Agreement [Member] \| Boeing 737400F [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated					2
Number of aircraft leased					2
Aircraft lease term					5 years
Notice period for termination of agreement											At any time under after the first anniversary of the commencement date of Aircraft with 90 day’s written notice
Aircraft option to extend agreement description											DHL has the option to extend the agreement with respect to one or more aircraft for a period of one year with 90 days’ advance written notice.

Summary of Significant Accounting Policies - Additional Information (Detail)			1 Months Ended			3 Months Ended			6 Months Ended
	Apr. 23, 2021 USD ($)	Apr. 15, 2021 USD ($)	Apr. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) Air-craft	Feb. 28, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) Air-craft	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of aircrafts operated \| Air-craft									163
Lease incentive assets				$ 4,800,000		$ 4,800,000			$ 4,800,000
Lease incentive obligations				4,200,000		4,200,000			4,200,000
Deferred revenue						4,900,000
Lease termination expense				4,500,000
Current and non-current deferred credit balances				5,200,000		5,200,000			5,200,000		$ 8,500,000
Recognized deferred credits within contract revenue						1,100,000		$ 1,900,000	900,000	$ 2,000,000.0
Deferred heavy maintenance balance, net of accumulated amortization				$ 1,200,000		1,200,000			1,200,000		$ 0
Engine overhaul expense						6,900,000		14,500,000	21,300,000	25,100,000
Engine overhaul pass-through expense						2,200,000		700,000	11,800,000	2,600,000
Airframe check expense						14,100,000		10,500,000	24,200,000	17,800,000
Airframe check pass-through expense						5,600,000		3,900,000	12,700,000	5,100,000
Payroll Support Program Extension, amount granted					$ 48,700,000
Payroll Support Program Extension, additional amount granted					7,300,000
Payroll Support Program Extension, total amount granted					$ 56,000,000.0
Payroll support government funds						$ 56,000,000.0			67,300,000
deferred payments							$ 11,300,000		$ 0
Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Payroll Support Program Extension, additional amount granted			$ 7,300,000
Third Payroll Support Program, eligible and estimated amount		$ 52,200,000
Third Payroll Support Program, amount received	$ 26,100,000
Aircraft [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage leased									10.00%
CRJ 700 [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft to be leased \| Air-craft				6
Number of aircrafts operated \| Air-craft				20
Operating lease, term of contract				9 years		9 years			9 years
Contract Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Lease revenue						$ 18,100,000		$ 52,400,000	$ 67,600,000	$ 105,700,000

Summary of Significant Accounting Policies - Schedule of Future Minimum Rental Income under Non-cancelable Operating Leases (Detail) $ in Thousands	Mar. 31, 2021 USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2021	$ 3,276
2022	6,552
2023	6,552
2024	6,552
2025	6,552
Thereafter	28,962
Total	$ 58,446

Summary of Significant Accounting Policies - Schedule of Deferred Revenue Remaining Performance Obligations (Detail) $ in Thousands	Mar. 31, 2021 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 33,858
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 675
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 9,097
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 9,430
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 9,169
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 3,695
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Maturities	$ 1,792
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year

Summary of Significant Accounting Policies - Schedule of Deferred Revenue Remaining Performance Obligations (Detail 1) $ in Thousands	Mar. 31, 2021 USD ($)
Revenue Performance Obligation Satisfied Over Time [Abstract]
Total Maturities	$ 33,858

Concentrations of Credit Risk - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Concentration Risk [Line Items]
Restricted cash	$ 3,351		$ 3,351		$ 3,446
Outstanding letters of credit to be collateralized by amounts on deposit	3,400		3,400
Allowance for doubtful accounts	$ 1,300		$ 1,300		$ 800
Sales Revenue, Net [Member] \| American Airlines Inc. [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	45.00%	51.00%	46.00%	51.00%
Sales Revenue, Net [Member] \| United [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	53.00%	49.00%	52.00%	49.00%

Intangible Assets - Information About Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Customer relationship	$ 43,800	$ 43,800
Accumulated amortization	(36,388)	(35,768)
Net carrying value	$ 7,412	$ 8,032

Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Amortization expense recognized	$ 0.3	$ 0.4	$ 0.6	$ 0.7
Amortization expense for remainder of 2021	0.6		0.6
Amortization expense for 2022	1.0		1.0
Amortization expense for 2023	0.9		0.9
Amortization expense for 2024	0.8		0.8
Amortization expense for 2025	$ 0.7		$ 0.7
Remaining weighted average term of intangible assets			14 years 7 months 6 days

Balance Sheet Information - Summary of Certain Significant Amounts Included in Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Expendable parts and supplies, net:
Expendable parts and supplies	$ 27,324	$ 27,431
Less: obsolescence and other	(4,280)	(4,460)
Expendable parts and supplies, net	23,044	22,971
Prepaid expenses and other current assets:
Deferred offering and reimbursed costs		1,261
Other	8,956	14,806
Prepaid expenses and other current assets	8,956	16,067
Property and equipment, net:
Property and equipment-gross	1,613,445	1,606,117
Less: accumulated depreciation	(432,761)	(393,702)
Property and equipment-net	1,180,684	1,212,415
Other Assets:
Warrants	16,374
Other	4,273
Other Assets	20,647	742
Other accrued expenses:
Accrued property taxes	5,996	11,354
Accrued interest	2,480	3,268
Accrued vacation	5,718	5,975
Other	14,416	24,881
Other accrued expenses	28,610	45,478
Aircraft and Other Flight Equipment Substantially Pledged [Member]
Property and equipment, net:
Property and equipment-gross	1,603,377	1,596,174
Other Machinery and Equipment [Member]
Property and equipment, net:
Property and equipment-gross	5,189	5,147
Leasehold Improvements [Member]
Property and equipment, net:
Property and equipment-gross	2,763	2,763
Vehicles [Member]
Property and equipment, net:
Property and equipment-gross	1,114	1,032
Building [Member]
Property and equipment, net:
Property and equipment-gross	699	699
Furniture and Fixtures [Member]
Property and equipment, net:
Property and equipment-gross	$ 303	$ 302

Balance Sheet Information - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Feb. 28, 2021	Feb. 10, 2021
Condensed Balance Sheet Statements Captions [Line Items]
Depreciation expense	$ 20,400	$ 20,100	$ 40,600	$ 40,300
Estimated initial equity warrant asset value						$ 16,400
Warrant asset value	$ 16,374		$ 16,374
Archer Aviation, Inc. [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Equity warrant assets, right to acquire common stock shares					1,171,649

Fair Value Measurements - Estimated Fair Value of Long-term Debt, Including Current Maturities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Long-term debt and financing leases, including current maturities, carrying value	$ 725,433	$ 743,250
Long-term debt and financing leases, including current maturities, fair value	$ 731,400	$ 768,700

Long-Term Debt, Financing Leases and Other Borrowings - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 725,433	$ 743,250
Less unamortized debt issuance costs	(10,598)
Less Notes payable warrants	(10,797)	(11,526)
Net long-term debt, including current maturities	704,038	731,724
Less current portion	(103,980)	(189,268)
Net long-term debt	600,058	542,456
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	22,930	22,930
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2022 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		41,472
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2024 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		55,674
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2027 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	106,092	105,887
Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	162,247	172,137
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2028 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	130,505	138,114
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		47,319
Senior and Subordinated Notes Payable to Secured Parties, Collateralized by the Underlying Aircraft, Due 2022 [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		29,682
Notes Payable to Financial Institution Due 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	1,523	1,523
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		4,182
Other Obligations Due to Financial Institution, Collateralized by the Underlying Equipment, Due 2023 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	5,663	6,864
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2024 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	54,573	63,341
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	39,375	48,125
Notes Payable to Financial Institution Due 2023 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	5,000	$ 6,000
Notes Payable to Financial Institution Due 2025 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 197,525

Long-Term Debt, Financing Leases and Other Borrowings - Schedule of Long-term Debt (Parenthetical) (Detail)					1 Months Ended					3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 12, 2020 USD ($) Air-craft	Oct. 30, 2020 USD ($)	Sep. 27, 2019 USD ($)	Sep. 25, 2019 USD ($)	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	Jun. 30, 2020 USD ($)	Dec. 31, 2019	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) Air-craft	Sep. 30, 2015 USD ($) Air-craft	Nov. 14, 2020 USD ($)	Nov. 13, 2020 USD ($)	Sep. 30, 2014 USD ($) Airfleet	Sep. 30, 2007 USD ($) Airfleet
Debt Instrument [Line Items]
Proceeds from long-term debt												$ 195,000,000	$ 23,000,000
Loan Agreement [Member]
Debt Instrument [Line Items]
Number of aircraft financed \| Air-craft	44
Repayments of long term debt	$ 167,700,000
Secured term loan facility, amount borrowed		$ 43,000,000
Secured term loan facility, additional amount borrowed																					$ 152,000,000
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%
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												monthly LIBOR plus 1.95%
Number of aircraft financed \| Airfleet																						10
Long term debt interest rate percentage																						1.95%
Repayments of long term debt																$ 40,000,000.0
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																		$ 246,000,000.0
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 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument maturity year												2020		2020
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2020 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument, face amount															$ 26,100,000	$ 26,100,000	$ 26,100,000	$ 26,100,000
Long term debt interest rate description												three-month LIBOR plus a spread ranging from 2.93% to 3.21%
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%	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															3.21%	3.21%	3.21%	3.21%
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%
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%
Other Obligations Due to Financial Institution, Collateralized by the Underlying Equipment, Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year												2023		2023
Imputed interest								9.128%
Number of spare engines leased \| Engine								2
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 Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument, face amount						$ 91,200,000
Long term debt interest rate description												monthly LIBOR plus 3.10%
Notes Payable to Financial Institution, Collateralized by the Underlying Equipment, Due 2024 [Member] \| Flight Equipment Maintenance [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 Aircraft [Member]
Debt Instrument [Line Items]
Debt instrument, face amount					$ 70,000,000.0
Long term debt interest rate description												monthly LIBOR plus 5.00%
Number of aircraft financed \| Airfleet					10
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member] \| CRJ-700 Aircraft [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate					5.25%						5.00%				5.25%
Notes Payable to Financial Institution Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year												2023		2023
Notes Payable to Financial Institution Due 2023 [Member] \| Flight Equipment Maintenance [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 8,000,000.0
Long term debt interest rate description												monthly LIBOR plus 5.00%
Notes Payable to Financial Institution Due 2023 [Member] \| Flight Equipment Maintenance [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate			5.25%								5.00%				5.25%
Notes Payable to Financial Institution Due 2025 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year												2025		2025
Senior Notes Due Two Thousand Twenty Seven [Member] \| CRJ-900 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount																			$ 151,000,000.0
Long term debt interest rate description												monthly LIBOR plus 2.71%
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																		$ 172,000,000.0
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 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%
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%
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%
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%
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%
Subordinated Notes DueTwoThousandTwentyTwo [Member] \| CRJ-900 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt interest rate percentage									4.50%
Working Capital Draw Loan [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 35,000,000.0
Long term debt interest rate description												one-month LIBOR plus 3.75%
Term loan, term				3 years
Debt instrument, expiration year and month				2022-09
Proceeds from long-term debt										$ 23,000,000.0		$ 22,900,000
Working Capital Draw Loan [Member] \| LIBOR [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate				3.75%
Secured Term Loan Facility [Member] \| Loan Agreement [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate		3.50%
Long term debt interest rate description												three-month LIBOR plus 3.50%
Secured term loan facility, maximum borrowing capacity		$ 200,000,000.0
Secured term loan facility, amount borrowed		$ 43,000,000.0
Secured term loan facility, additional amount borrowed																				$ 0	$ 152,000,000.0
Debt instrument, maturity date		Oct. 30, 2025										Oct. 30, 2025

Long-Term Debt, Financing Leases and Other Borrowings - Schedule of Principal Maturities of Long-term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Long Term Debt By Maturity [Abstract]
Remainder of 2021	$ 59,013
2022	113,682
2023	89,462
2024	61,209
2025	56,526
Thereafter	345,541
Long-term debt	$ 725,433	$ 743,250

Long-Term Debt, Financing Leases and Other Borrowings - Additional Information (Detail)					3 Months Ended	6 Months Ended
	Nov. 13, 2020 USD ($)	Nov. 12, 2020 USD ($) Air-craft	Oct. 30, 2020 USD ($) $ / shares shares	Sep. 25, 2019 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2021 USD ($) $ / shares	Mar. 31, 2020 USD ($)	Nov. 14, 2020 USD ($)	Sep. 30, 2020 USD ($)	Apr. 09, 2020 $ / shares
Debt Instrument [Line Items]
Property and equipment, net						$ 1,180,684,000			$ 1,212,415,000
Long-Term Debt						704,038,000			$ 731,724,000
Proceeds from long-term debt						$ 195,000,000	$ 23,000,000
Warrants of common stock exercise price \| $ / shares						$ 0.004				$ 3.98
Maximum [Member]
Debt Instrument [Line Items]
Calculated collateral coverage ratio			1.6
Minimum [Member]
Debt Instrument [Line Items]
Additional collateral coverage ratio			1.6
Loan Agreement [Member]
Debt Instrument [Line Items]
Secured term loan facility, amount borrowed			$ 43,000,000
Secured term loan facility, additional amount borrowed	$ 152,000,000
Warrants to purchase shares of common stock \| shares			4,899,497
Warrants of common stock exercise price \| $ / shares			$ 3.98
Debt issuance costs allocated to warrants						$ 100,000
Repayments of long term debt		$ 167,700,000
Number of aircraft financed \| Air-craft		44
Loan Agreement [Member] \| $43M Treasury Loan [Member]
Debt Instrument [Line Items]
Capitalized debt issuance costs, net			$ 700,000
Loan Agreement [Member] \| $152M Treasury Loan [Member]
Debt Instrument [Line Items]
Capitalized debt issuance costs, net	2,300,000
Loan Agreement [Member] \| EDC Loans [Member]
Debt Instrument [Line Items]
Debt issuance costs	3,100,000
Repayments of long term debt	1,000,000.0
Payment of loans		$ 164,100,000
Discount for balance amount of loans		$ 3,600,000
Debt discount	2,500,000
Equipment Notes [Member]
Debt Instrument [Line Items]
Long-Term Debt						$ 162,200,000
Working Capital Draw Loan [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 35,000,000.0
Term loan, term				3 years
Debt instrument, expiration year and month				2022-09
Long term debt interest rate description						one-month LIBOR plus 3.75%
Proceeds from long-term debt					$ 23,000,000.0	$ 22,900,000
Working Capital Draw Loan [Member] \| Revolving Credit Facility [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate				3.75%
Secured Term Loan Facility [Member] \| Loan Agreement [Member]
Debt Instrument [Line Items]
Long term debt interest rate description						three-month LIBOR plus 3.50%
Long term debt, basis spread on variable rate			3.50%
Secured term loan facility, maximum borrowing capacity			$ 200,000,000.0
Secured term loan facility, amount borrowed			$ 43,000,000.0
Secured term loan facility, additional amount borrowed	152,000,000.0							$ 0
Debt instrument, maturity date			Oct. 30, 2025			Oct. 30, 2025
Secured Term Loan Facility [Member] \| Loan Agreement [Member] \| $43M Treasury Loan [Member]
Debt Instrument [Line Items]
Secured term loan facility, amount borrowed			$ 43,000,000.0
Secured Term Loan Facility [Member] \| Loan Agreement [Member] \| $152M Treasury Loan [Member]
Debt Instrument [Line Items]
Secured term loan facility, additional amount borrowed	$ 152,000,000.0							$ 0
Aircraft and Equipment [Member] \| Pledged as Collateral [Member]
Debt Instrument [Line Items]
Property and equipment, net						$ 1,060,000,000.0

Earnings Per Share and Equity - Calculations of Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share And Equity [Abstract]
Net income	$ 5,689	$ 14,118	$ 1,885	$ 10,785	$ 19,807	$ 12,670
Basic weighted average common shares outstanding	35,628		35,141		35,579	35,082
Add: Incremental shares for:
Dilutive share adjustment - UST Warrant	3,038				2,183	138
Dilutive share adjustment - Restricted Shares	766		124		620
Diluted weighted average common shares outstanding	39,432		35,265		38,382	35,220
Net income per common share attributable to Mesa Air Group:
Basic	$ 0.16		$ 0.05		$ 0.56	$ 0.36
Diluted	$ 0.14		$ 0.05		$ 0.52	$ 0.36

Earnings Per Share and Equity - Additional Information (Detail) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restricted Stock [Member]
Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted loss per share	0	0
Number of Warrants [Member]
Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted loss per share	0	0

Common Stock - Additional Information (Detail)			6 Months Ended
Common Stock - Additional Information (Detail)	Apr. 09, 2019	Aug. 08, 2018 shares	Mar. 31, 2021 $ / shares shares	Sep. 30, 2020 shares	Apr. 09, 2020 $ / shares
Class of Warrant or Right [Line Items]
Warrants term			5 years
Warrants of common stock exercise price \| $ / shares			$ 0.004		$ 3.98
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
Common stock, warrants issued			4,899,497	0
Common stock, warrants outstanding			4,899,497	0
2018 Equity Incentive Plan [Member]
Class of Warrant or Right [Line Items]
Common stock, stock split			2.5-for-1 stock split effected
Stock split ratio	2.5
Increase in number of shares authorized for issuance		1,000,000

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Income Taxes [Line Items]
Effective tax rate (ETR) from continuing operations	24.90%	40.90%	25.30%	27.60%
Statutory federal tax rate				21.00%
State net operating loss carryforwards					$ 0.7
Domestic Tax Authority [Member] \| 2027-2038 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					512.4
State and Local Jurisdiction [Member] \| 2021-2040 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					$ 223.9
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					2021
Maximum [Member] \| Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year					2038
Maximum [Member] \| State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year					2040

Share-Based Compensation and Stock Repurchases - Schedule of Restricted Share Activity (Detail) - Restricted Stock [Member]	6 Months Ended
	Mar. 31, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance \| shares	1,195,548
Number of Shares, Granted \| shares	121,688
Number of Shares, Vested \| shares	(132,109)
Number of Shares, Forfeited \| shares	(17,500)
Number of Shares, Unvested, Ending Balance \| shares	1,167,627
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance \| $ / shares	$ 5.47
Weighted-Average Grant Date Fair Value, Granted \| $ / shares	8.58
Weighted-Average Grant Date Fair Value, Vested \| $ / shares	8.75
Weighted-Average Grant Date Fair Value, Forfeited \| $ / shares	4.90
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance \| $ / shares	$ 5.44

Share-Based Compensation and Stock Repurchases - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested share-based compensation arrangements	$ 4,400				$ 4,400
Unrecognized compensation cost, period for recognition					2 years 3 months 18 days
Share-based compensation expense	800		$ 1,200		$ 1,700	$ 2,500
Repurchased shares, value	$ 157	$ 19	$ 160	$ 41
Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period					1 year
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
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchased shares, shares					175,925
Repurchased shares, value					$ 200

Employee Stock Purchase Plan - Additional Information (Detail) - 2019 ESPP [Member]	6 Months Ended
	Mar. 31, 2021 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares, discount rate	10.00%
Number of ordinary shares issued	157,714
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 and Contingencies - Additional Information (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021 USD ($) Air-craft	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($) Air-craft Engine Lawsuit	Mar. 31, 2020 USD ($)
Purchase Commitment Excluding Longterm Commitment [Line Items]
Number of leased aircraft \| Air-craft	17		17
Aggregate rental expense under all operating aircraft, equipment and facility leases \| $	$ 13.9	$ 18.6	$ 27.7	$ 35.4
Weighted average remaining lease term Operating leases	3 years 1 month 6 days		3 years 1 month 6 days
Weighted average discount rate Operating leases	4.20%		4.20%
IPO [Member]
Purchase Commitment Excluding Longterm Commitment [Line Items]
Number of putative class action lawsuits \| Lawsuit			2
Superior Court of State of Arizona [Member] \| IPO [Member]
Purchase Commitment Excluding Longterm Commitment [Line Items]
Number of putative class action lawsuits \| Lawsuit			1
U.S. District Court of Arizona [Member] \| IPO [Member]
Purchase Commitment Excluding Longterm Commitment [Line Items]
Number of putative class action lawsuits \| Lawsuit			1
CF34-8C5 or CF34-8E5 Engines [Member] \| Letter Agreement No. 13-3 [Member]
Purchase Commitment Excluding Longterm Commitment [Line Items]
Number of new spare engines to be acquired \| Engine			10
New spare engines delivery month and year description			The Company agreed to purchase and take delivery of 10 new CF34-8C5 or CF34-8E5 engines with delivery dates starting from July 1, 2021 through November 1, 2022. During the quarter ended March 31, 2021, a $7.0 million non-refundable purchase deposit was made for the first five engines to be delivered in calendar 2021.
Purchase deposit \| $	$ 7.0		$ 7.0
Number of new spare engines to be delivered \| Engine			5
Purchase commitment amount \| $	$ 50.0		$ 50.0