Mesa Air (MESA) 10-Q 24 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2023	Feb. 01, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
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	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		40,940,326

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Current assets:
Cash and cash equivalents	$ 16,068	$ 32,940
Restricted cash	3,134	3,132
Receivables, net ($1,265 and $4,016 from related party)	5,517	8,253
Expendable parts and supplies, net	28,830	29,245
Assets held for sale	92,260	57,722
Prepaid expenses and other current assets	4,476	7,294
Total current assets	150,285	138,586
Property and equipment, net	534,459	698,022
Lease and equipment deposits	1,630	1,630
Operating lease right-of-use assets	8,959	9,709
Deferred heavy maintenance, net	7,200	7,974
Assets held for sale	40,336	12,000
Other assets	32,764	30,546
Total assets	775,633	898,467
Current liabilities:
Current portion of long-term debt and finance leases ($19,335 and $20,500 from related party)	156,789	163,550
Current portion of deferred revenue	3,983	4,880
Current maturities of operating leases	3,240	3,510
Accounts payable	54,451	58,957
Accrued compensation	7,657	10,008
Other accrued expenses	27,774	27,001
Total current liabilities	253,894	267,906
Noncurrent liabilities:
Long-term debt and finance leases, excluding current portion ($36,795 and $30,630 from related party)	315,464	364,728
Noncurrent operating lease liabilities	7,706	8,077
Deferred credits from related party	4,464	4,617
Deferred income taxes	8,842	8,414
Deferred revenue, net of current portion	14,062	16,167
Other noncurrent liabilities	28,589	28,522
Total noncurrent liabilities	379,127	430,525
Total liabilities	633,021	698,431
Commitments and contingencies (Note 15)
Stockholders' equity:
Common stock of no par value and additional paid-in capital, 125,000,000 shares authorized; 40,940,326 (2024) and 40,940,326 (2023) shares issued and outstanding, 4,899,497 (2024) and 4,899,497 (2023) warrants issued and outstanding	271,581	271,155
Accumulated deficit	(128,969)	(71,119)
Total stockholders' equity	142,612	200,036
Total liabilities and stockholders' equity	$ 775,633	$ 898,467

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Non current portion of long-term debt from related party	$ 28,589	$ 28,522
Common stock, no par value	$ 0	$ 0
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	40,940,326	40,940,326
Common stock, shares outstanding	40,940,326	40,940,326
Common stock, warrants issued	4,899,497	4,899,497
Common stock, warrants outstanding	4,899,497	4,899,497
Related Party [Member]
Recievables from related party	$ 1,265	$ 4,016
Current portion of long-term debt from related party	19,335	20,500
Non current portion of long-term debt from related party	$ 36,795	$ 30,630

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating revenues:
Contract revenue	$ 118,777	$ 147,173
Operating expenses:
Flight operations	51,818	58,320
Maintenance	48,627	48,287
Aircraft rent	1,204	4,083
General and administrative	12,009	13,988
Depreciation and amortization	13,293	15,203
Asset impairment	40,384	3,719
Loss on sale of assets	386
(Gain) on extinguishment of debt	(2,954)
Other operating expenses	2,458	1,126
Total operating expenses	167,225	144,726
Operating income/(loss)	(48,448)	2,447
Other income (expense), net:
Interest expense	(11,160)	(11,276)
Interest income	14	71
Unrealized gain/(loss) on investments, net	2,451	(1,679)
Other income (expense), net	157	417
Total other expense, net	(8,538)	(12,467)
Loss before taxes	(56,986)	(10,020)
Income tax expense/(benefit)	864	(930)
Net loss and comprehensive loss	$ (57,850)	$ (9,090)
Net loss per share attributable to common shareholders
Basic	$ (1.41)	$ (0.25)
Diluted	$ (1.41)	$ (0.25)
Weighted-average common shares outstanding
Basic	40,940	36,378
Diluted	40,940	36,378
Contract Revenue
Operating revenues:
Contract revenue	$ 101,100	$ 128,450
Pass Through and Other Revenue
Operating revenues:
Contract revenue	$ 17,677	$ 18,723

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Related Party [Member]
Contract revenue, Related party	$ 96,412	$ 59,370

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Number of Warrants [Member]	Common Stock and Additional Paid-In Capital [Member]	Retained Earnings [Member]
Beginning balance at Sep. 30, 2022	$ 308,174			$ 259,177	$ 48,997
Beginning balance, shares at Sep. 30, 2022		36,376,897	4,899,497
Stock compensation expense	688			688
Payment of tax withholding for RSUs	(1)			(1)
Payment of tax withholding for RSUs, shares		(847)
Restricted shares issued, shares		2,500
Net loss	(9,090)				(9,090)
Ending balance at Dec. 31, 2022	299,771			259,864	39,907
Ending balance, shares at Dec. 31, 2022		36,378,550	4,899,497
Beginning balance at Sep. 30, 2023	200,036			271,155	(71,119)
Beginning balance, shares at Sep. 30, 2023		40,940,326	4,899,497
Stock compensation expense	427			427
Net loss	(57,850)				(57,850)
Ending balance at Dec. 31, 2023	$ 142,612			$ 271,582	$ (128,969)
Ending balance, shares at Dec. 31, 2023		40,940,326	4,899,497

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (57,850)	$ (9,090)
Adjustments to reconcile net loss to net cash flows provided by (used in) operating activities:
Depreciation and amortization	13,293	15,203
Stock compensation expense	427	688
Unrealized (gain)/loss on investments, net	(2,451)	1,679
Deferred income taxes	428	(1,014)
Amortization of deferred credits	(153)	(213)
Amortization of debt discount and issuance costs and accretion of interest into long-term debt	2,291	1,379
Asset impairment	40,384	3,719
(Gain)/loss on sale of assets	386
(Gain) on extinguishment of debt	(2,954)
Other	912	55
Changes in assets and liabilities:
Receivables	2,736	(9,137)
Expendable parts and supplies	415	1,150
Prepaid expenses and other operating assets and liabilities	2,604	2,290
Accounts payable	(3,903)	(7,008)
Deferred revenue	(3,002)	(5,256)
Accrued expenses and other liabilities	(1,513)	(656)
Operating lease right-of-use assets and liabilities	109	177
Net cash used in operating activities	(7,841)	(6,034)
Cash flows from investing activities:
Capital expenditures	(6,884)	(16,740)
Proceeds from sale of aircraft and engines	53,489
Refund (payment) of equipment and other deposits		131
Net cash provided by (used in) investing activities	46,605	(16,609)
Cash flows from financing activities:
Proceeds from long-term debt	81,855	39,000
Principal payments on long-term debt and finance leases	(137,489)	(17,544)
Payments of debt and warrant issuance costs	0	(417)
Payment of tax withholding for RSUs	0	(1)
Net cash (used in) provided by financing activities	(55,634)	21,038
Net change in cash, cash equivalents and restricted cash	(16,870)	(1,605)
Cash, cash equivalents and restricted cash at beginning of period	36,072	61,025
Cash, cash equivalents and restricted cash at end of period	19,202	59,420
Supplemental cash flow information
Cash paid for interest	6,948	7,763
Cash paid for income taxes , net	0	0
Operating lease payments in operating cash flows	1,211	4,679
Supplemental non-cash operating activities
Right-of-use assets obtained in exchange for lease liabilities	$ 339	236
Supplemental non-cash financing activities
Finance lease obtained in exchange for lease liability		$ 76,185

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (57,850)	$ (9,090)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Rule 10b5-1 Arrangement Modified	false
Non-Rule 10b5-1 Arrangement Modified	false

Organization and Operations

Organization and Operations	3 Months Ended
	Dec. 31, 2023
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", the "Company", "we", "our", or "us") is the holding company of Mesa Airlines, a regional air carrier providing scheduled passenger service to 82 cities in 36 states, the District of Columbia, Canada, Cuba, and Mexico as well as cargo services out of Cincinnati/Northern Kentucky International Airport. Mesa operated or maintained as operational spares a fleet of 80 regional aircraft with approximately 280 daily departures and 2,246 employees as of December 31, 2023. Mesa’s fleet were conducted under the Company’s Capacity Purchase Agreement ("CPA") and Flight Services Agreement ("FSA"), leased to a third party, held for sale, or maintained as operational spares. Mesa operates all of its flights as either United Express or DHL Express flights pursuant to the terms of the CPA entered into United and FSA with DHL (each, our “major partner”). Except as set forth in the following sentence, all of the Company’s consolidated contract revenues for the three months ended December 31, 2023 and December 31, 2022 were derived from operations associated with the CPA, FSA, and leases of aircraft to a third party. Revenues during the period ended December 31, 2022 also included revenues derived from our CPA with American Airlines, Inc. ("American"), which terminated in April 2023. The United CPA involves a revenue-guarantee arrangement whereby United 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. United also pays certain expenses directly to suppliers, such as fuel, ground operations and landing fees. Under the terms of the CPA, United controls route selection, pricing, and seat inventories, reducing our exposure to fluctuations in passenger traffic, fare levels, and fuel prices. Under our FSA with DHL, we receive a fee per block hour with a minimum block hour guarantee in exchange for providing cargo flight services. Ground support expenses including fueling and airport fees are paid directly by DHL. Impact of Pilot Shortage and Transition of Operations to United During our three months ended December 31, 2023 and fiscal year ended September 30, 2023 , the severity of the pilot shortage, elevated pilot attrition, the transition of our operations with American to United, and increasing costs associated with pilot wages adversely impacted our financial results, cash flows, financial position, and other key financial ratios. One of the primary factors contributing to the pilot shortage and attrition is the demand for pilots at major carriers, which are hiring at an accelerated rate. These airlines now seek to increase their capacity to meet the growing demand for air travel. A primary source of pilots for the major U.S. passenger and cargo carriers are the U.S. regional airlines. As a result of the pilot shortage and attrition, the Company has increased overall hourly pay of nearly 118 % for captains and 172 % for new hires. As a result of pilot shortage, we produced less block hours to generate revenues. During the three months ended December 31, 2023 , these challenges resulted in a negative impact on the Company’s financial results highlighted by cash flows used in operations of $ 7.8 million and net loss of $ 57.9 million, including a non-cash impairment charge of $ 40.4 million related to the Company designating eight CRJ-900 aircraft, 11 CRJ-900 airframes (without engines), and 48 spare engines as held for sale. These conditions and events raised financial concerns about our ability to continue to fund our operations and meet our debt obligations over the next twelve months from the filing of this Form 10-Q. To address such concerns, management developed and implemented several material changes to our business designed to ensure the Company could continue to fund its operations and meet its debt obligations over the next twelve months. The Company implemented the following measures during the three months ended December 31, 2023. • We have 15 aircraft under the RASPRO finance lease with a buyout obligation of $ 50.3 million at the end of March 2024. We entered into purchase agreements with two separate parties to purchase the RASPRO aircraft and related engines. One agreement is for 30 engines for a total of $ 19.5 million. The second agreement is for 15 airframes (without engines) for a total of $ 18.8 million. Both of these transactions are expected to be completed by the end of September 2024, with net cash from these transactions expected to be approximately $( 12.1 ) million. Subsequent to December 31, 2023, the Company entered into a binding Memorandum with RASPRO to defer the $ 50.3 million buyout obligation until September 2024, subject to the payment of certain commitment fee amounts which are due in May, July, and August, along with certain RASPRO Trust administration fee amounts. See note 16 for additional disclosure regarding the binding Memorandum. • The Company closed the sale of the remaining four aircraft during the three months ended December 31, 2023 as part of an agreement entered into with a third party for the sale of 11 CRJ-900 aircraft. We previously reported on the sale of seven of the aircraft in our 2023 Form 10-K. Gross proceeds from the sale of the remaining four aircraft was $ 12.0 million. Net proceeds from the sale of all four aircraft was $ 6.5 million after partial debt reduction of our loan with the United States Department of the Treasury (the "UST Loan"). • The Company closed the sale of the remaining four aircraft during the three months ended December 31, 2023 as part of an agreement entered into with American for the sale of seven CRJ-900 aircraft. Gross proceeds from the sale of the remaining four aircraft was $ 41.5 million. Net proceeds from the sale of all four aircraft was $ 5.7 million after the retirement of our loan with Export Development Bank of Canada ("EDC Loan") and the junior note with MHIRJ ("MHIRJ junior note"). MHIRJ had previously agreed to forgive approximately $ 5.0 million in principal contingent upon the repayment of $ 4.2 million in principal by December 31, 2023. $ 0.6 million in proceeds from the sale of each aircraft was repaid to MHIRJ for a total of $ 4.2 million, and we achieved approximately $ 5.0 million of forgiveness on the MHIRJ junior note. • On January 11, 2024 and January 19, 2024, we entered into the First Amendment to our Third Amended and Restated United CPA and the Second Amendment to our Third Amended and Restated United CPA (the "January 2024 United CPA Amendments"), respectively. The January 2024 United CPA Amendments provide additional liquidity and certain other amendments described below: o Increased CPA rates, retroactive to October 1, 2023 through December 31, 2024. We generated an additional approximately $ 20.4 million in incremental revenue from October 1, 2023 through April 30, 2024, and are projected to generate an additional $ 26.8 million in incremental revenue from May 1, 2024 through December 31, 2024. We received additional payments of $ 8.8 million in January related to the block hour rate increase from October 1, 2023 through December 31, 2023, and $ 21.3 million in additional payments related to the block hour rate increase from October 1, 2023 through April 30, 2024. o Amended certain notice requirements for removal by United of up to eight CRJ-900 Covered Aircraft (as defined in the United CPA) from the United CPA. o Extended United's existing utilization waiver for the Company's operation of E-175 and CRJ-900 Covered Aircraft (as defined in the United CPA) to June 30, 2024. • On January 11, 2024 and January 19, 2024, we entered into Amendment No. 4 to our Second Amended and Restated Credit and Guaranty Agreement, Amendment No. 1 to Stock Pledge Agreement and Limited Waiver of Conditions to Credit Extension and Waiver and Amendment No. 5 to our Second Amended and Restated Credit and Guaranty Agreement (collectively, the "January 2024 Credit Agreement Amendments"), respectively. The January 2024 Credit Agreement Amendments provide for the following: o The repayment in full of the Company's $ 10.5 million Effective Date Bridge Loan obligations, and the prepayment (and corresponding reduction) of approximately $ 2.1 million in Revolving Loans (as defined therein), with the proceeds from the sale, assignment, or transfer of the Company's vested investment in Heart Aerospace Incorporated. Subsequent to December 31, 2023, the Company transferred its vested investment in Heart Aerospace Incorporated to United and realized a gain on the investment of $ 7.2 million. o As a result of the repayment of the Effective Date Bridge Loan and pay down of the Revolving Loans, the shares of capital stock of Archer Aviation, Inc. held by the Company were released as collateral for the United credit facility, as provided in Amendment No. 4. o The waiver of certain financial covenant defaults with respect to the fiscal quarters ended June 30, 2023, September 30, 2023, and December 31, 2023 and the waiver of projected financial covenant defaults with respect to the fiscal quarter ending March 31, 2024. o An increase in the Applicable Margin (as defined in the United credit facility) during a specified period of time for borrowings under the Credit Agreement. o Loan prepayment requirements in connection with the sale of four specified aircraft engines and the addition of such engines as collateral for the United credit facility for a specified period of time. • On May 8, 2024, we entered into a Waiver Agreement to our Second Amended and Restated Credit and Guaranty Agreement providing for the waiver of a certain projected financial covenant default with respect to the fiscal quarter ending June 30, 2024. • On December 1, 2023, we entered into an agreement with a third party to sell 12 surplus GE model CF34-8C aircraft engines and related parts. Subsequent to December 31, 2023, we closed the sale of all 12 engines for gross proceeds of $ 54.2 million and $ 15.9 million of net proceeds after the retirement of debt. • We entered into a purchase agreement with a third party which provides for the sale of 23 spare engines for gross proceeds of $ 11.5 million which will be used to pay down our UST Loan. The transaction is expected to close by the end of December 2024. • In addition to already executed agreements to sell aircraft, the Company is actively seeking arrangements to sell other surplus assets primarily related to the CRJ fleet including aircraft, engines, and spare parts to reduce debt and optimize operations. • We have delayed and/or deferred major spending on aircraft and engine maintenance to match the current and projected level of flight activity. The Company believes the plans and initiatives outlined above have effectively alleviated the financial concerns and will allow the Company to meet its cash obligations for the next twelve months following the issuance of its financial statements. On April 22, 2024, the Company entered into a binding Memorandum that provides for the payment of certain commitment fee amounts by the Company, which are due in May, July, and August, along with certain RASPRO Trust administration fee amounts, in consideration for the deferral of the buyout obligation until September 2024. Certain of the commitment fee amounts and Trust fees otherwise payable will be waived if the Company completes its purchase obligations with respect to all 15 airframes and 30 engines as set forth in the Memorandum. The terms agreed to in the Memorandum will be set forth in a definitive lease amendment to be entered into by the parties. The forecast of undiscounted cash flows prepared to determine if the Company has the ability to meet its cash obligations over the next twelve months was prepared with significant judgment and estimates of future cash flows based on projections of CPA and FSA block hours, maintenance events, labor costs, and other relevant factors. Assumptions used in the forecast may change or not occur as expected. As of December 31, 2023, the Company has $ 156.8 million of principal maturity payments on long-term debt due within the next twelve months. We plan to meet these obligations with our cash on hand, ongoing cashflows from our operations, as well as the liquidity created from the additional measures identified above. If our plans are not realized, we intend to explore additional opportunities to create liquidity by refinancing and deferring repayment of our principal maturity payments that are due within the next twelve months. The Company continues to monitor covenant compliance with its lenders as any noncompliance could have a material impact on the Company’s financial position, cash flows and results of operations. United Capacity Purchase Agreement Under the United CPA, we have the ability to fly up to 80 aircraft for United. The aircraft can be a mix of any number of E-175, or CRJ-900 aircraft so long as the number of aircraft operating at any given time does not exceed 80 . As of December 31, 2023, we operated 54 E-175 and 26 CRJ-900 aircraft under our Third Amended and Restated Capacity Purchase Agreement with United dated December 27, 2022, which amended and restated the Second Amended and Restated Capacity Purchase Agreement dated November 4, 2020 (as amended, the “United CPA” or the "Amended and Restated United CPA"). Under the United CPA, United owns 42 of our 60 E-175 aircraft. The E-175 aircraft owned by United and leased to us have terms expiring between 2024 and 2028 , and the 18 E-175 aircraft owned by us have terms expiring in 2028 . In exchange for providing flight services under our United CPA, 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. United reimburses us on a pass-through basis for certain costs related to heavy airframe and engine maintenance, landing gear, auxiliary power units ("APUs") and component maintenance for the aircraft owned by United. Our United CPA permits United, subject to certain conditions, including the payment of certain costs tied to aircraft type, to terminate the agreement in its discretion, or remove aircraft from service, by giving us notice of 90 days or more . If United elects to terminate our United CPA in its entirety or permanently remove select aircraft from service, we are permitted to return any of the affected aircraft leased from United at no cost to us. In addition, if United removes any of our 18 owned E-175 aircraft from service at its direction, United would remain obligated, at our option, to assume the aircraft ownership and associated debt with respect to such aircraft through the end of the term of the United CPA. On December 27, 2022, we entered into the Amended and Restated United CPA, which provides, among other things, for the following amended terms: • The addition of up to 38 CRJ-900 aircraft to be operated by the Company on behalf of United under the Amended and Restated United CPA, dependent on the number of E-175 aircraft the Company is operating. As of December 31, 2023 , we operated 26 CRJ-900 aircraft under our Amended and Restated United CPA; • An increase in rates to cover the Company’s pilot pay increases instituted in September 2022, effective through September 2025; • United to be responsible for all costs associated with converting the CRJ-900 aircraft for operation in United’s network; • Terms providing that United may remove the CRJ-900 aircraft from the scope of the United CPA, subject to certain notice and other requirements; • United's existing utilization waiver for the Company’s operation of E-175LL Covered Aircraft (as defined in the United CPA) to be extended to December 31, 2023; • The extension of existing monthly operational performance incentives; and • An agreement by the Company to not enter into new regional air carrier service agreements, excluding the Company’s existing agreement with DHL, and provided that this restriction shall not apply from and after the earlier to occur of (i) January 1, 2026 and (ii) the Company's satisfaction of certain Performance Milestones (as defined in the Amended and Restated United CPA). In January 2024, the Amended and Restated United CPA was amended with the January 2024 United CPA Amendments which provide for the following: • Increased CPA rates, retroactive to October 1, 2023 through December 31, 2024; • Amended certain notice requirements for removal by United of up to eight CRJ-900 Covered Aircraft (as defined in the United CPA) from the United CPA; • Extended United's existing utilization waiver for the Company's operation of E-175 and CRJ-900 Covered Aircraft (as defined in the United CPA) to June 30, 2024. Additionally, in January 2023, in consideration for entering in the Amended and Restated United CPA and providing the revolving line of credit, discussed in Note 8, the Company (i) granted United the right to designate one individual to the Company's board of directors (the "United Designee"), which occurred effective May 2, 2023 with the appointment of Jonathan Ireland and (ii) issued to United 4,042,061 shares of the Company’s common stock equal to approximately 10 % of the Company’s issued and outstanding capital stock on such date (the "United Shares"). United's board designee rights will terminate at such time as United's equity ownership in the Company falls below five percent (5%) of the Company's issued and outstanding stock. United was also granted pre-emptive rights relating to the issuance of any equity securities by the Company and certain registration rights, set forth in a definitive registration rights agreement with United, granting United customary demand registration rights in respect of publicly registered offerings of the Company, subject to usual and customary exceptions and limitations. Pursuant to the United CPA, we agreed to lease our CRJ-700 aircraft to another United Express service provider for a term of nine years . We ceased operating our CRJ-700 fleet in February 2021 in connection with the transfer of those aircraft into a lease agreement. During August of 2022, we committed to a formal plan to sell 18 of our CRJ-700 aircraft and terminated the leases on the 18 CRJ-700 aircraft, which have all subsequently been sold. Our United CPA is subject to termination prior to its expiration, including under the following circumstances: • If certain operational performance factors fall below a specified percentage for a specified time, subject to notice under certain circumstances; • If we fail to perform the material covenants, agreements, terms or conditions of our United CPA or similar agreements with United, subject to 30 days' notice and cure rights; • If either United or we become insolvent, file bankruptcy, or fail to pay debts when due, the non-defaulting party may terminate the agreement; • If we merge with, or if control of us is acquired by another air carrier or a corporation directly or indirectly owning or controlling another air carrier; • United, subject to certain conditions, including the payment of certain costs tied to aircraft type, may terminate the agreement in its discretion, or remove E-175 aircraft from service, by giving us notice of 90 days or more ; and • If United elects to terminate our United CPA in its entirety or permanently remove aircraft from service, we are permitted to return any of the affected E-175 aircraft leased from United at no cost to us. On February 29, 2024, March 29, 2024, April 1, 2024, April 19, 2024, and April 30, 2024, we received individual notices from United exercising its right under Section 2.4(a) of the United CPA to remove a total of 10 CRJ-900 Covered Aircraft (as defined in the United CPA), effective as follows: two aircraft - March 31, 2024; two aircraft - April 30, 2024; one aircraft - May 21, 2024; one aircraft - May 31, 2024; two aircraft - June 30, 2024; and two aircraft - July 31, 2024. DHL Flight Services Agreement On December 20, 2019, we entered into a Flight Services Agreement with DHL (the “DHL FSA”). Under the terms of the DHL FSA, we operate four Boeing 737 aircraft which are leased to us from DHL and a third party to provide cargo air transportation services as of December 31, 2023. In exchange for providing cargo flight services, we receive a fee per block hour with a minimum block hour guarantee. We are eligible for a monthly performance bonus or subject to a monthly penalty based on timeliness and completion performance. Ground support expenses including fueling and airport fees are paid directly by DHL. Under our DHL FSA, DHL leases two Boeing 737-400F aircraft and one 737-800F 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 life limited parts (“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 us. A third Boeing 737-400F aircraft is leased to us under an operating lease by a third party. The DHL FSA expires five years from the commencement date of the first aircraft placed into service, which was in October 2020. 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 FSA is subject to the following termination rights prior to its expiration: • If either party fails to comply with the obligations, warranties, representations, or undertakings under the DHL FSA, subject to certain notice and cure rights; • If either party is declared bankrupt or insolvent; • If we are unable to legally operate the aircraft under the DHL FSA for a specified number of days; • At any time after the first anniversary of the commencement date of the first aircraft placed in service with 90 days' written notice. • If we fail to comply with performance standards for three (3) consecutive measurement periods. • If we are subject to a labor incident that materially and adversely affects our ability to perform services under the DHL FSA for a specified number of days; • Upon a change in control or ownership of the Company; and • 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 at our expense, or if the aircraft becomes unavailable for more than 30 days due to unscheduled maintenance. In February 2024, we mutually agreed to the consensual wind-down of our flight operations on behalf of DHL and ceased all such operations on March 1, 2024.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Dec. 31, 2023
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 GAAP 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. 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, 2023 included in the Company's Annual Report on Form 10-K for the year ended September 30, 2023 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. Segment Reporting As of December 31, 2023 , our chief operating decision maker was the Chief Executive Officer. While we operate under a capacity purchase agreement and a flight services agreement, 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 and allocate resources, 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 Revenue We recognize contract revenue when the service is provided under our CPA and FSA. Under the CPA and FSA, our major partners generally pay for each departure, flight hour or block hour incurred, and an amount per aircraft in service each month with additional incentives or penalties based on flight completion, on-time performance, and other operating metrics. Our performance obligation is met as each flight is completed, and revenue is recognized and reflected in contract revenue. We recognize pass-through revenue when the service is provided under our CPA and FSA. Pass-through revenue represents reimbursements for certain direct expenses incurred including passenger liability and hull insurance, property taxes, other direct costs defined within the agreements, and major maintenance on aircraft leased from our major partners at nominal rates. Our 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. We record deferred revenue when cash payments are received or are due from our major partners in advance of our performance. During the three months ended December 31, 2023, we recognized approximately $ 3.0 million of previously deferred revenue. Deferred revenue is recognized as flights are completed over the remaining terms of the respective contracts. The deferred revenue balance as of December 31, 2023 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 December 31, Total Deferred Revenue 2024 (remainder of) $ 2,139 2025 5,733 2026 4,350 2027 4,093 2028 1,625 Thereafter 105 Total $ 18,045 A portion of our compensation under our CPA with United is designed to reimburse the Company for certain aircraft ownership costs. Such costs include aircraft principal and interest debt service costs, aircraft depreciation, and interest expense or aircraft lease expense costs while the aircraft is under contract. We have concluded this component of the compensation under these agreements is lease revenue, as such agreements identify the "right of use" of a specific type and number of aircraft over a stated period of time. We account for the non-lease component under ASC 606 and account for the lease component under ASC 842. We allocate the consideration in the contract between the lease and non-lease components based on their stated contract prices, which is based on a cost basis approach representing our estimate of the stand-alone selling prices. The lease revenue associated with our CPA is accounted for as an operating lease and is reflected as contract revenue in the condensed consolidated statements of operations and comprehensive loss. We recognized $ 34.9 million and $ 41.1 million of lease revenue for the three months ended December 31, 2023 and December 31, 2022, respectively. We have not separately stated aircraft rental income in the condensed consolidated statements of operations and comprehensive loss because the use of the aircraft is not a separate activity from the total service provided under our CPA. Historically, the Company had lease agreements with GoJet Airlines LLC (“GoJet”) to lease 20 CRJ-700 aircraft. The lease agreements are accounted for as operating leases and have a term of nine ( 9 ) years beginning on the delivery date of each aircraft. 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 contract revenue. Lease revenue for supplemental rent is deferred and recognized within contract revenue when it is probable that amounts received will not be reimbursed for future qualifying maintenance events over the lease term. The Company mitigated 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 leases have specified lease return condition requirements and we maintain inspection rights under the leases. Lease incentive obligations for reimbursements of certain aircraft maintenance costs are recognized as lease incentive assets and were amortized on a straight-line basis and recognized as a reduction to lease revenue over the lease term. During fiscal year 2022, the Company terminated its lease agreements with GoJet to lease 18 of the 20 CRJ-700 aircraft and classified the 18 aircraft as assets held for sale. All 18 aircraft were sold as of December 31, 2023. The remaining two lease agreements are accounted for as finance leases. The following table summarizes future minimum rental payments under operating leases related to leased aircraft that had remaining non-cancelable lease terms as of December 31, 2023 (in thousands): Periods Ending December 31, Total Payments 2024 (remainder of) $ 1,638 2025 2,184 2026 2,184 2027 2,184 2028 2,184 Thereafter 5,824 Total $ 16,198 Leases We determine if an arrangement is a lease at inception. As a lessee, we have lease agreements with lease and non-lease components and have elected to account for such components as a single lease component. Our operating lease activities are recorded in operating lease right-of-use assets, current maturities of operating leases, and noncurrent operating lease liabilities in the condensed consolidated balance sheets. Finance leases are reflected in property and equipment, net, current portion of long-term debt and finance leases, and long-term debt and finance leases, excluding current portion in the condensed consolidated balance sheets. Right-of-use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. Certain variable lease payments are not included in the calculation of the right-of-use assets and lease liability due to uncertainty of the payment amount and are recorded as lease expense in the period incurred. In determining the present value of lease payments, we use either the implicit rate in the lease when it is readily determinable or our estimated incremental borrowing rate, based on information available at the lease commencement. Our lease terms include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Operating lease costs are recognized on a straight-line basis over the lease term, while finance leases result in a front-loaded expense pattern. As a lessee, we have elected a short-term lease practical expedient on all classes of underlying assets, permitting us to not apply the recognition requirements of ASC 842 to leases with terms of 12 months or less. We lease, at nominal rates, certain aircraft from United and DHL under our CPA and FSA, which are excluded from operating lease assets and liabilities as they do not represent embedded leases under ASC 842. Other than such leases at nominal amounts, 18 of our aircraft are leased from third parties. In the event that we or one of our major 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 are written off. Contract Liabilities Contract liabilities consist of deferred credits for cost reimbursements from major partners related to aircraft modifications and pilot training associated with the capacity purchase agreement. The deferred credits are recognized over time depicting the pattern of the transfer of control of services resulting in ratable recognition of revenue over the remaining term of the capacity purchase agreement. Current and non-current deferred credits are recorded in other accrued expenses and non-current deferred credits in the condensed consolidated balance sheets. Our total current and non-current deferred credit balances at December 31, 2023 and September 30, 2023 were $ 4.9 million and $ 5.1 million, respectively. We recognized $ 1.0 million and $ 0.2 million of the deferred credits within contract revenue during the three months ended December 31, 2023 and December 31, 2022 , respectively. Maintenance Expense We operate 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. We account 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 $ 0.8 million and $ 0.8 million for the three months ended December 31, 2023 and December 31, 2022, respectively. As of December 31, 2023 and September 30, 2023, our deferred heavy maintenance balance, net of accumulated amortization, was $ 7.2 million and $ 8.0 million, respectively. We account for heavy maintenance and major overhaul costs for all other fleets under the direct expense method whereby 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 $ 5.8 million and $ 8.7 million for the three months ended December 31, 2023 and December 31, 2022, respectively, of which $ 5.7 million and $ 8.7 million, respectively, was pass-through expense. Airframe C-check expense totaled $ 6.4 million and $ 5.1 million for the three months ended December 31, 2023 and December 31, 2022, respectively, of which $ 3.8 million and $ 4.4 million, respectively, was pass-through expense. Assets Held for Sale We classify assets as held for sale when our management approves and commits to a formal plan of sale that is probable of being completed within one year. Assets designated as held for sale are recorded at the lower of their current carrying value or their fair market value, less costs to sell, beginning in the period in which the assets meet the criteria to be classified as held for sale. See Note 5 for further discussion of our assets classified as held for sale as of December 31, 2023 .

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Dec. 31, 2023
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. The U.S. Federal Reserve, in conjunction with the Alternative Reference Rates Committee, has determined that the U.S. dollar LIBOR will be replaced by the Secured Overnight Financing Rate (SOFR). Optional expedients can be applied through December 31, 2024. Under the expedient, the Company will account for amendments to agreements as if the modification was not substantial. The new carrying amounts of debts will consist of the carrying amount of the original debt and any additional fees associated with the modified debt instrument. A new effective yield will be established based on the new carrying amount and revised cash flows. In June 2022, the FASB issued new guidance to clarify the fair value measurement guidance for equity securities subject to contractual restrictions that prohibit the sale of an equity security. Further, the guidance introduces new disclosure requirements for equity securities subject to contractual sale restrictions that are measured at fair value. The standard will be effective for annual reporting periods beginning after December 15, 2023, including interim reporting periods within those fiscal years. We are currently evaluating the impact that the new guidance will have on our consolidated financial statements.

Concentrations of Credit Risk

Concentrations of Credit Risk	3 Months Ended
	Dec. 31, 2023
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. We maintain our cash accounts with high credit quality financial institutions and, accordingly, minimal credit risk exists with respect to the financial institutions. As of December 31, 2023, we had $ 3.1 million in restricted cash. We have an agreement with a financial institution for a 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 terms of this agreement, $ 3.1 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 our total revenue or net accounts receivable balance at each respective balance sheet date. All of our revenue for the three months ended December 31, 2023 and December 31, 2022 was derived from the American and United CPAs, DHL FSA, and from leases of our CRJ-700 aircraft to GoJet. Substantially all of our accounts receivable at December 31, 2023 and September 30, 2023 was derived from these agreements. American accounted for 0 % and approximately 45 % of our total revenue for the three months ended December 31, 2023 and December 31, 2022, respectively. United accounted for approximately 96 % and 50 % of our total revenue for the three months ended December 31, 2023 and December 31, 2022, respectively. The wind-down period of the American CPA ended on April 3, 2023, at which the American CPA was officially terminated. A termination of the United CPA would have a material adverse effect on our business prospects, financial condition, results of operations, and cash flows. Amounts billed under our agreements are subject to our interpretation of the applicable agreement and are subject to audit by our major partners. Periodically, our major 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 partner. As such, we review amounts due based on historical collection trends, the financial condition of the major partners, and current external market factors and record a reserve for amounts estimated to be uncollectible in accordance with the applicable guidance for expected credit losses. Our allowance for doubtful accounts was no t material as of December 31, 2023 or September 30, 2023 . If our ability to collect these receivables and the financial viability of our major partners is materially different than estimated, our estimate of the allowance for credit losses could be materially impacted.

Assets Held for Sale

Assets Held for Sale	3 Months Ended
	Dec. 31, 2023
Discontinued Operations and Disposal Groups [Abstract]
Assets Held for Sale	5. Assets Held for Sale During 2022, our management committed to a formal plan to sell certain of our CRJ-900, CRJ-200, and CRJ-700 aircraft. Accordingly, we determined the aircraft met the criteria to be classified as assets held for sale and have separately presented them in our condensed consolidated balance sheet at the lower of their current carrying value or their fair market value less costs to sell. The fair values are based upon observable and unobservable inputs, including recent purchase offers and market trends and conditions. The assumptions used to determine the fair value of our assets held for sale are subject to inherent uncertainty and could produce a wide range of outcomes which we will continue to monitor in future periods as new information becomes available. Prior to the ultimate sale of the assets, subsequent changes in our estimate of the fair value of our assets held for sale will be recorded as a gain or loss with a corresponding adjustment to the assets’ carrying value. As of September 30, 2023, the Company had 15 CRJ-900 aircraft classified as held for sale with a net book value of $ 69.7 million, $ 57.7 million was classified as classified as current assets on our condensed consolidated balance sheet and $ 12.0 million of which was classified as noncurrent assets on our condensed consolidated balance sheet. During the three months ended December 31, 2023 , the Company closed the sale of four CRJ-900 aircraft to American for gross proceeds of $ 41.5 million. Net proceeds from the sale of all four aircraft was $ 5.7 million after the retirement of the EDC Loan and MHIRJ junior note. Additionally, during the three months ended December 31, 2023, the Company closed the sale of four CRJ-900 aircraft to a third party for gross proceeds of $ 12.0 million. Net proceeds from the sale of all four aircraft was $ 6.5 million after partial debt reduction on the UST Loan. The sale of these assets reduced the total held for sale balance by $ 53.9 million, $ 41.9 million of which reduced the balance of current held for sale assets and $ 12.0 million of which reduced the balance of noncurrent held for sale assets. During the three months ended December 31, 2023 , eight CRJ-900 aircraft, 11 CRJ-900 airframes (without engines), and 48 GE model CF34-8C engines were designated as held for sale. The Company wrote down the value of the assets with signed purchase agreements to the agreed upon sales price, which approximates fair value, and wrote down the value of held for sale assets with no signed agreement to a third party appraisal value. The Company reclassified $ 111.7 million to held for sale related to these assets, $ 71.4 million of which is classified as current assets on our condensed consolidated balance sheet and $ 40.3 million of which is classified as noncurrent assets on our condensed consolidated balance sheet. The Company recorded an impairment loss of $ 45.5 million on the assets designated as held for sale during the three months ended December 31, 2023, which was slightly offset by a $ 5.1 million impairment gain due to fair value adjustments on assets previously designated as held for sale. The total impairment loss related to held for sale assets during the three months ended December 31, 2023 was $ 40.4 million. As of December 31, 2023 , the Company has 15 CRJ-900 aircraft, 11 CRJ-900 airframes (without engines), and 48 engines that are classified as assets held for sale with a net book value of $ 132.6 million, $ 92.3 million of which is classified as current assets on our condensed consolidated balance sheet and $ 40.3 million of which is classified as noncurrent assets on our condensed consolidated balance sheet. The following table summarizes the Company's held for sale activity during the three months ended December 31, 2023 (in millions): Total Current Assets Noncurrent Assets Held for sale balance as of September 30, 2023 $ 69.7 $ 57.7 $ 12.0 Assets sold ( 53.9 ) ( 41.9 ) ( 12.0 ) Assets reclassified to held for sale 111.7 71.4 40.3 Impairment gain due to fair value adjustments 5.1 5.1 — Held for sale balance as of December 31, 2023 $ 132.6 $ 92.3 $ 40.3

Balance Sheet Information

Balance Sheet Information	3 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Information	6. Balance Sheet Information Certain significant amounts included in the condensed consolidated balance sheets consisted of the following (in thousands): December 31, September 30, 2023 2023 Expendable parts and supplies, net: Expendable parts and supplies $ 40,215 $ 39,630 Less: expendable parts warranty ( 7,218 ) ( 6,295 ) Less: obsolescence ( 4,167 ) ( 4,090 ) $ 28,830 $ 29,245 Prepaid expenses and other current assets: Prepaid aviation insurance $ 1,596 $ 3,176 Prepaid vendors 896 143 Prepaid other insurance 761 1,205 Lease incentives 143 1,125 Prepaid fuel and other 1,080 1,645 $ 4,476 $ 7,294 Property and equipment, net: Aircraft and other flight equipment $ 779,436 $ 1,039,782 Other equipment 9,467 9,421 Total property and equipment 788,903 1,049,203 Less: accumulated depreciation ( 254,444 ) ( 351,181 ) $ 534,459 $ 698,022 Other assets: Investments in equity securities $ 23,021 $ 20,320 Lease incentives 919 954 Contract asset 8,309 8,756 Other 515 516 $ 32,764 $ 30,546 Other accrued expenses: Accrued property taxes $ 3,052 $ 5,281 Accrued interest 5,099 3,447 Accrued vacation 6,933 6,763 Accrued lodging 3,165 3,984 Accrued maintenance 1,546 2,117 Accrued simulator costs 242 1,006 Accrued employee benefits 1,681 1,450 Accrued fleet operating expense 1,668 650 Other 4,388 2,303 $ 27,774 $ 27,001 Other noncurrent liabilities: Warrant liabilities $ 25,225 $ 25,225 Lease incentive obligations 1,050 1,050 Long-term employee benefits 495 429 Other 1,819 1,818 $ 28,589 $ 28,522 Impairment of Long-lived Assets The Company monitors for any indicators of impairment of the long-lived fixed assets. When certain conditions or changes in the economic situation exist, the assets may be impaired and the carrying amount of the assets exceed their fair value. The assets are then tested for recoverability of carrying amount. 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 net 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. We group assets at the capacity purchase agreement, flight services agreement, and fleet-type level (i.e., the lowest level for which there are identifiable cash flows). If impairment indicators exist with respect to any of the asset groups, we estimate future cash flows based on projections of capacity purchase or flight services agreement, block hours, maintenance events, labor costs and other relevant factors. During the fiscal year ended September 30, 2023, due to the impacts of the pilot shortage and the pilot wage increase, the Company assessed whether any indicators of impairment existed in any of our long-lived asset groups. The Company concluded that the net book value of our United asset group was fully recoverable and did not record any impairment. During the three months ended December 31, 2023 , eight CRJ-900 aircraft, 11 CRJ-900 airframes (without engines), and 48 GE model CF34-7C engines were reclassified to held for sale and evaluated for impairment. The Company determined that the carrying value of the assets exceeded their estimated fair value and recognized an impairment loss of $ 40.4 million during the three months ended December 31, 2023 related to the held for sale aircraft. The Company determined that no other indicators of impairment were present during the quarter and no further steps were determined to be necessary. The Company’s assumptions about future conditions relevant to the assessment of potential impairment of its long-lived assets 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. Depreciation Expense on Property and Equipment: Depreciation of property and equipment totaled $ 13.3 million and $ 14.4 million for the three months ended December 31, 2023 and December 31, 2022, 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 a number shares of common stock in Archer Aviation, Inc. (“Archer”), which at the time of our initial investment was a private, venture-backed company. As the initial investment in Archer did not have a readily determinable fair value, we accounted for this investment using the measurement alternative under ASC 321, Investments – Equity Securities, and measured 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 estimated the initial equity warrant asset value to be $ 16.4 million based on publicly available information as of the grant date. In September 2021, the merger between Archer and a special purpose acquisition company (“SPAC”) was completed, resulting in a readily determinable fair value of our investments in Archer. Accordingly, gains and losses associated with changes in the fair value of our investments in Archer are reported in earnings, in accordance with ASC 321. The initial grant date values 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 aircraft purchase agreement. In connection with closing of the merger between Archer and the SPAC described above, in September 2021, we purchased 500,000 Class A common shares in Archer for $ 5.0 million and obtained an additional warrant to purchase shares of Archer with a total grant date value of $ 5.6 million. The initial value of the warrants was recognized as a vendor credit liability within other noncurrent liabilities, and will be settled in the future, as a reduction of the acquisition date value of the eVTOL aircraft contemplated in the related aircraft purchase agreement. Because these investments have readily determinable fair values, gains and losses resulting from changes in fair value of the investments are reflected in earnings, in accordance with ASC 321. All of our vested warrants have been exercised into shares of Archer common stock. The fair values of the Company’s investments in Archer are Level 1 within the fair value hierarchy as the values are determined using quoted prices for the equity securities. The Company recorded a $ 2.5 million unrealized gain on the investment in Archer during the three months ended December 31, 2023. The total value of the investment in Archer is $ 13.9 million as of December 31, 2023. In connection with a negotiated forward purchase contract for fully electric aircraft executed in July 2021, we obtained $ 5.0 million of preferred stock in Heart Aerospace Incorporated (“Heart”), a privately held company. Our investment in Heart does not have a readily determinable fair value, so we account for the investment using the measurement alternative under ASC 321 and measure the investment at initial 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 change to fair value is warranted. Any changes in fair value from the initial cost of the investment in preferred stock are recognized as increases or decreases on our balance sheet and as net gains or losses on investments in equity securities. The initial investment in preferred stock was measured at cost of $ 5.0 million. Subsequent to December 31, 2023, the Company transferred its vested investment in Heart to United and realized a gain on the investment of $ 7.2 million. In connection with a negotiated forward purchase contract for hybrid-electric vertical takeoff and landing (“VTOL”) aircraft executed in February 2022, we obtained a warrant giving us the right to acquire a number of shares of common stock in the privately-held manufacturer of the VTOL aircraft. These investments 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 value of the warrant assets will be recognized as increases or decreases to the investment on our balance sheet and as net gains or losses on investments in equity securities. We estimated the initial warrant asset value to be $ 3.2 million based on prices of similar investments in the same issuer. The grant date value of the warrants, $ 3.2 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 VTOL aircraft contemplated in the related forward purchase agreement. On March 12, 2024, the privately-held manufacturer of the VTOL aircraft, XTI Aerospace, Inc ("XTIA")., and its merger subsidiary completed their merger agreement, and began trading as XTIA on the Nasdaq Composite on March 13, 2024, resulting in a readily determinable fair value on our investment in XTIA. The fair values of the Company's investments in XTIA are now Level 1 within the fair value hierarchy as the values are determined using quoted prices for the equity securities. Total net gain/(loss) on our investments in equity securities totaled $ 2.5 million and $( 1.7 ) million for the three months ended December 31, 2023 and December 31, 2022, respectively, and are reflected in unrealized gain/(loss) on investments, net in our condensed consolidated statements of operations and comprehensive loss. As of December 31, 2023 and September 30, 2023, the aggregate carrying amount of our investments in equity securities was $ 23.0 million and $ 20.3 million, respectively, and the carrying amount of our investments without readily determinable fair values was $ 8.8 million and $ 8.8 million, respectively.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. Fair Value Measurements Fair value is an exit price representing the amount that would be received to sell an asset, or paid to transfer a liability, in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Accounting standards include disclosure requirements relating to the fair values used for certain financial instruments and establish a fair value hierarchy. The hierarchy prioritizes valuation inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market. Each fair value measurement is reported in one of three levels: Level 1 — Observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2 — Inputs, other than quoted prices in active markets, which are observable either directly or indirectly; and Level 3 — Unobservable inputs in which there is little or no market data, requiring an entity to develop its own assumptions. Other than our assets held for sale and investments in equity securities described in Notes 5 and 6, respectively, we did not measure any of our assets or liabilities at fair value on a recurring or nonrecurring basis as of December 31, 2023 and September 30, 2023. 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. Our debt agreements are not traded on an active market. We have determined the estimated fair value of our 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. We utilize the discounted cash flow method to estimate the fair value of Level 3 debt. The carrying value and estimated fair value of our total long-term debt and finance leases, including current maturities, were as follows (in millions): December 31, 2023 September 30, 2023 Carrying Fair Carrying Fair Value Value Value Value Long-term debt and finance leases, including current maturities (1) $ 481.0 $ 456.0 $ 538.3 $ 493.6 (1) Current and prior period long-term debts' carrying and fair values exclude net debt issuance costs.

Long-Term Debt, Finance Leases,

Long-Term Debt, Finance Leases, and Other Borrowings	3 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Long-Term Debt, Finance Leases, and Other Borrowings	8. Long-Term Debt, Finance Leases, and Other Borrowings Long-term debt as of December 31, 2023 and September 30, 2023, consisted of the following (in thousands): December 31, September 30, 2023 2023 Senior and subordinated notes payable to secured parties, due in monthly installments, interest based on SOFR plus interest spread at 2.71 % through 2027 , collateralized by the underlying aircraft $ - $ 39,018 Notes payable to secured parties, due in semi-annual installments, interest based on SOFR plus interest spread at 4.75 % to 6.25 % through 2028 , collateralized by the underlying aircraft 108,815 108,815 Notes payable to secured parties, due in quarterly installments, interest based on SOFR plus interest at spread 2.20 % to 2.32 % for senior note & 4.50 % for subordinated note through 2028 , collateralized by the underlying aircraft 86,194 90,401 Revolving credit facility, quarterly interest based on SOFR plus interest spread at 4.50 % through 2028 , with incentives for up to $ 15 million based on achieving certain performance metrics 45,630 40,630 United Bridge Loan - due in quarterly installments based on SOFR plus interest spread at 4.50 % through 2024 10,500 10,500 Other obligations due to financial institution, monthly and/or quarterly interest due from 2022 through 2031 , collateralized by the underlying equipment 68,540 67,637 Notes payable to financial institution, due in monthly installments, interest based on SOFR plus interest spread at 3.10 % through 2024 , collateralized by the underlying equipment 271 1,075 Notes payable to financial institution, due in monthly installments, interest based on fixed interest of 7.50 %, through 2024 , collateralized by the underlying equipment 38,846 41,098 Notes payable to financial institution, quarterly interest based on SOFR plus interest spread at 3.50 % through 2027 122,155 139,100 Gross long-term debt, including current maturities 480,951 538,274 Less unamortized debt issuance costs ( 4,383 ) ( 5,083 ) Less notes payable warrants ( 4,315 ) ( 4,913 ) Net long-term debt, including current maturities 472,253 528,278 Less current portion, net of unamortized debt issuance costs ( 156,789 ) ( 163,550 ) Net long-term debt $ 315,464 $ 364,728 Principal maturities of long-term debt as of December 31, 2023, and for each of the next five years are as follows (in thousands): Periods Ending December 31, Total Principal 2024 (remainder of) $ 152,275 2025 49,263 2026 172,700 2027 51,313 2028 30,878 Thereafter 24,522 $ 480,951 The carrying value of collateralized aircraft and equipment as of December 31, 2023 was approximately $ 586.6 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. As of December 31, 2023, we had $ 108.8 million of equipment notes outstanding issued under the EETC financing included in long-term debt in 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. We evaluated whether the pass-through trust formed for the EETC financing is a Variable Interest Entity ("VIE") and required to be consolidated. We have determined we do not have a variable interest in the pass-through trust, and therefore, we have not consolidated the pass-through trust with our financial statements. United Revolving Credit Facility On December 27, 2022, in connection with entering into the Amended and Restated United CPA, (i) United agreed to purchase and assume all of First Citizens’ rights and obligations as a lender under the Existing Facility pursuant to an Assignment and Assumption Agreement, (ii) United and CIT Bank agreed to amend the Existing Facility pursuant to an Amendment No. 1, dated December 27, 2022 (“Amendment No. 1”), and an Amendment No. 2, dated January 27, 2023 (“Amendment No. 2”; the Existing Facility as amended by Amendment No. 1 and Amendment No. 2, the "Amended Facility"), and (iii) Wilmington Trust, National Association agreed to assume all of CIT Bank’s rights and obligations as Administrative Agent pursuant to an Agency Resignation, Appointment and Assumption Agreement, dated as of January 27, 2023. Amendment No. 1, among other things, extends the Maturity Date from the earlier to occur of November 30, 2028, or the date of the termination of the Amended and Restated United CPA; provides for a revolving loan of $ 10.5 million plus fees and expenses, which is due January 31, 2024, subject to certain mandatory prepayment requirements; provides for Revolving Commitments equal to $ 30.7 million plus the original principal amount of the $ 10.5 million revolving loan; amortization of the obligations outstanding under the existing CIT Agreement commencing quarterly until March 31, 2025; and a covenant capping Restricted Payments (as defined in the Amended Facility) at $ 5.0 million per fiscal year, a consolidated interest and rental coverage ratio of 1.00 to 1.00 covenant, and a Liquidity (as defined in the Amended Facility) requirement of not less than $ 15.0 million at the close of any business day. Interest assessed under the Amended Facility is 3.50 % for Base Rate Loans and 4.50 % for Term SOFR Loans (as such terms are defined in the Amended Facility). Amendment No. 2, among other things, amends the definition of Controlled Account (as defined in the Amended Facility). Amounts borrowed under this Amended Facility are secured by a collateral pool consisting of a combination of expendable parts, rotable parts and engines and a pledge of the Company’s stock in certain aviation companies. United funded $ 25.5 million as of the closing date of Amendment No. 1, to be used for general corporate purposes. The United line of credit contains an additional deemed prepayment of $ 15 million with potential forgiveness upon the achievement of a certain number of block hours as well as maintaining a CCF of at least 99.3 % over any rolling four-month period from April 2023 through December 2025. In order to earn forgiveness on the deemed prepayment, we must also have repaid the bridge loan in full. As of December 31, 2023, we have achieved $ 9.75 million in forgiveness. Subsequent to December 31, 2023, we earned an additional $ 0.75 million in forgiveness. As the bridge loan is still outstanding as of December 31, 2023, the forgiveness is not currently recognizable. However, subsequent to December 31, 2023, the Company repaid our bridge loan in full, and the $ 10.5 million in forgiveness achieved was recognized as a deemed prepayment. $ 4.5 million of the deemed prepayment remains outstanding. On September 6, 2023, the Company amended the existing United Credit Facility to (i) permit the Company to re-draw approximately $ 7.9 million of the Effective Date Bridge Loan (as defined in the United Credit Facility) previously repaid; (ii) increased the amount of Revolving Commitments (as defined in the United Credit Facility) from $ 30.7 million to $ 50.7 million, in each case, plus the original principal amount of the Effective Date Bridge Loan and subject to the Borrowing Base (as defined in the United Credit Facility); and (iii) amended the calculation of the Borrowing Base. Amounts borrowed under this facility bear interest at 3.50 % for Base Rate Loans and 4.50 % per annum for Term SOFR Loans. Amounts borrowed under the Amended Credit Facility are secured by a collateral pool consisting of a combination of expendable parts, rotable parts and engines, a pledge of certain of the Company’s bank accounts and a pledge of the Company’s stock in certain aviation companies. As of May 23, 2024, the Company has $ 2.2 million available to draw on the line of credit. On January 11, 2024 and January 19, 2024, we entered into Amendment No. 4 to our Second Amended and Restated Credit and Guaranty Agreement, Amendment No. 1 to Stock Pledge Agreement and Limited Waiver of Conditions to Credit Extension ("Amendment No. 4") and Waiver and Amendment No. 5 to our Second Amended and Restated Credit and Guaranty Agreement (collectively, the "January 2024 Credit Agreement Amendments"), respectively. The January 2024 Credit Agreement Amendments provide for the following: • The repayment in full of the Company's $ 10.5 million Effective Date Bridge Loan obligations, and the prepayment (and corresponding reduction) of approximately $ 2.1 million in Revolving Loans (as defined therein), with the proceeds from the sale, assignment, or transfer of the Company's vested investment in Heart Aerospace Incorporated. • As a result of the repayment of the Effective Date Bridge Loan and pay down of the Revolving Loans, the shares of capital stock of Archer Aviation, Inc. held by the Company are being released as collateral for the United credit facility, subject to certain conditions. • The waiver of certain financial covenant defaults with respect to the fiscal quarters ended June 30, 2023, September 30, 2023, and December 31, 2023 and the waiver of projected financial covenant defaults with respect to the fiscal quarter ending March 31, 2024. • An increase in the Applicable Margin (as defined in the United credit facility) during a specified period of time for borrowings under the Credit Agreement. • Loan prepayment requirements in connection with the sale of four specified aircraft engines and the addition of such engines as collateral for the United credit facility for a specified period of time. On May 8, 2024, we entered into a Waiver Agreement to our Second Amended and Restated Credit and Guaranty Agreement providing for the waiver of a certain projected financial covenant default with respect to the fiscal quarter ending June 30, 2024. Loan Agreement with the United States Department of the Treasury On October 30, 2020, we entered into a loan and guarantee agreement with the U.S. Department of the Treasury (the “U.S. Treasury”) for a secured loan facility of up to $ 200.0 million that matures in October 2025 (“the Treasury Loan”). During the first quarter of fiscal 2021, we borrowed an aggregate of $ 195.0 million. No further borrowings are available under the Treasury Loan. The Treasury Loan bears interest at a variable rate equal to (a)(i) the SOFR rate divided by (ii) one minus the Eurodollar Reserve Percentage plus (b) 3.50 %. Accrued interest on the loans is payable in arrears, or paid-in-kind by increasing the principal balance of the loan by such interest payment, on the first business day following the 14 th day of each March, June, September, and December. All principal amounts outstanding under the Treasury Loan are due and payable in a single installment on October 30, 2025 . Commencing in June 2022, we initiated the payment of interest in lieu of increasing the principal amount of the loan. Our obligations under the Treasury Loan are secured by certain aircraft, aircraft engines, accounts receivable, ground service equipment, flight simulators, and tooling (collectively, the “Collateral”). The obligations under the Treasury Loan are guaranteed by the Company and Mesa Air Group Inventory Management. The proceeds were used for general corporate purposes and operating expenses, to the extent permitted by the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”). Voluntary prepayments of the Treasury Loan may be made, in whole or in part, without premium or penalty, at any time and from time to time. Amounts prepaid may not be reborrowed. Mandatory prepayments of the Treasury Loan 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 Treasury Loan) occurs with respect to Mesa Airlines, we will be required to repay the loans outstanding under the Treasury Loan. The Treasury Loan requires us, under certain circumstances, including within 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 1.55 to 1.0, we are required either to provide additional Collateral (which may include cash collateral) to secure the obligations under the Treasury Loan or repay the term loans under the Treasury Loan, in such amounts that the recalculated collateral coverage ratio, after giving effect to any such additional Collateral or repayment, is at least 1.55 to 1.0. The Treasury Loan contains two (2) financial covenants, a minimum collateral coverage ratio and a minimum liquidity level. The Treasury Loan 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, we are 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 Treasury Loan and as partial compensation to the U.S. Treasury for the provision of financial assistance under the Treasury Loan, we issued to the U.S. Treasury warrants to purchase an aggregate of 4,899,497 shares of our common stock at an exercise price of $ 3.98 per share, which was the closing price of the common stock 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 our option. The fair value of the warrants was estimated using a Black-Scholes option pricing model and recorded in stockholders' equity with an offsetting debt discount to the Treasury Loan in the condensed consolidated balance sheets. Spare Engine Financing In December 2021, we entered into a loan agreement with a financing institution to finance certain purchases of spare engines via a newly formed limited liability company (“LLC”). The loan agreement provides for aggregate borrowings of up to $ 54.0 million through November 2022. In December 2021, we borrowed an aggregate of $ 35.3 million under the loan agreement, which matures in December 2027 . The borrowed amounts are collateralized by the underlying engines and require monthly principal and interest payments until maturity. In December 2022, the agreement was amended for the borrowings under the loan agreement to bear a fixed interest rate of 7.5 %. The borrowings are the obligation of the newly formed LLC and are guaranteed by Mesa Airlines, Inc. The newly formed LLC, which is wholly owned by Mesa, was determined to be a VIE for which we are the primary beneficiary because we have the power to direct the activities of the LLC that most significantly impact the LLC’s economic performance and the obligation to absorb losses and right to receive benefits from the LLC in our capacity as sole member of the LLC and guarantor of the borrowings. Therefore, the LLC is consolidated in our financial statements and the borrowings are reflected as long-term debt in our condensed consolidated balance sheets. The loan agreement contains a loan-to-value (“LTV”) financial covenant pursuant to which we are required to prepay certain amounts of the loan if the aggregate outstanding principal balance of the loan exceeds a specified percentage of the appraised value of the engines beginning in the 12 th full month after closing and each June 1 and December 1 thereafter.

Loss Per Share

Loss Per Share	3 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Loss Per Share	9. Loss Per Share Calculations of net loss per common share were as follows (in thousands): Three Months Ended December 31, 2023 2022 Net loss $ ( 57,850 ) $ ( 9,090 ) Basic weighted average common shares outstanding 40,940 36,378 Diluted weighted average common shares outstanding 40,940 36,378 Net loss per common share attributable to Mesa Air Group: Basic $ ( 1.41 ) $ ( 0.25 ) Diluted $ ( 1.41 ) $ ( 0.25 ) Basic income or loss per common share is computed by dividing net income or loss 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 is calculated by applying the treasury stock method. Share-based awards and warrants whose impact is anti-dilutive under the treasury stock method are 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.

Common Stock

Common Stock	3 Months Ended
	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Common Stock	10. Common Stock As discussed in Note 8, we issued warrants to the U.S. Treasury to purchase shares of our common stock, no par value, at an exercise price of $ 3.98 per share. The exercise price and number of 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 our option. The warrants were accounted for within equity at a grant date fair value determined under the Black-Scholes option pricing model . As of December 31, 2023 , 4,899,497 warrants were issued and outstanding. We have not historically paid dividends on shares of our common stock. Additionally, the Treasury Loan and our aircraft lease facility with RASPRO Trust 2005, a pass-through trust, contain restrictions that limit our ability to or prohibit us from paying dividends to holders of our common stock.

Income Taxes

Income Taxes	3 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes Our effective tax rate ("ETR") from continuing operations was - 1.5 % and 9.3 % for the three months ended December 31, 2023 and 2022, respectively. The Company’s ETR during the three months ended December 31, 2023 decreased from the prior year tax rate, primarily as a result of certain permanent tax differences, state taxes, and changes in the valuation allowance against federal and state net operating losses. We continue to maintain a valuation allowance on a portion of our federal and state net operating losses in jurisdictions with shortened carryforward periods or in jurisdictions where our operations have significantly decreased as compared to prior years in which the net operating losses were generated. As of December 31, 2023 , the Company had aggregate federal and state net operating loss carryforwards of approximately $ 560.0 million and $ 247.0 million, respectively, which expire in 2030 - 2038 and 2024 - 2043 , respectively. Approximately $ 4.5 million of state net operating loss carryforwards are expected to expire in the current fiscal year.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation	12. Share-Based Compensation Restricted Stock We grant restricted stock units (“RSUs”) as part of our long-term incentive compensation to employees and non-employee members of the Board of Directors. RSUs generally vest over a period of three to five years for employees and 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. The restricted share activity for the three months ended December 31, 2023 is summarized as follows: Weighted- Average Number Grant Date of Shares Fair Value Restricted shares unvested at September 30, 2023 736,891 $ 3.35 Granted — $ — Vested — $ — Forfeited ( 8,000 ) $ 4.72 Restricted shares unvested at December 31, 2023 728,891 $ 3.33 As of December 31, 2023, there was $ 1.3 million of total unrecognized compensation cost related to unvested share-based compensation arrangements, which is expected to be recognized over a weighted-average period of 1.5 years. Compensation cost for share-based awards is recognized on a straight-line basis over the vesting period. Share-based compensation expense for the three months ended December 31, 2023 and December 31, 2022 was $ 0.4 million and $ 0.7 million, respectively. Shares for Restricted Stock Units Tax Withholding The amounts remitted for employee withholding taxes during the three months ended December 31, 2023 and December 31, 2022 were zero and $ 1.0 thousand, respectively, for which the Company withheld zero and 847 shares of our common stock, respectively, that were underlying the RSUs that vested.

Employee Stock Purchase Plan

Employee Stock Purchase Plan	3 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Employee Stock Purchase Plan	13. Employee Stock Purchase Plan 2019 ESPP The Mesa Air Group, Inc. 2019 Employee Stock Purchase Plan ( "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 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 December 31, 2023, eligible employees purchased and we issued an aggregate of 444,590 Mesa Air Group, Inc. ordinary shares under the 2019 ESPP.

Leases

Leases	3 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	14. Leases As of December 31, 2023, we leased 18 aircraft, airport facilities, office space, and other property and equipment under non-cancelable operating and finance leases. The leases generally require us to pay all taxes, maintenance, insurance, and other operating expenses. Operating leased expense is recognized as a rental expense on a straight-line basis over the lease term, net of lessor rebates and other incentives. Finance lease is capitalized and depreciated over the useful life of the asset. Aggregate rental expense under all aircraft, equipment and facility leases totaled approximately $ 8.0 million and $ 6.9 million for the three months ended December 31, 2023 and December 31, 2022, respectively. The components of our lease costs were as follows (in thousands): Three Months Ended December 31, 2023 2022 Operating lease costs $ 1,278 $ 4,699 Variable and short-term lease costs 1,279 889 Interest expense on finance lease liabilities 1,289 274 Amortization expense of finance lease assets 4,123 1,046 Total lease costs $ 7,969 $ 6,907 As of December 31, 2023, our operating leases have a remaining weighted average lease term of 6.2 years and our operating lease liabilities were measured using a weighted average discount rate of 5.8 % . RASPRO Lease Facility Historically, Mesa Airlines, as lessee, entered into the RASPRO Lease Facility, with RASPRO as lessor, for 15 of our CRJ-900 aircraft classified as operating leases. The obligations under the RASPRO Lease Facility are guaranteed by us, and basic rent is paid quarterly on each aircraft. During December 2022, the Company entered into an agreement with RASPRO Trust, reducing the buyout pricing on all 15 aircraft at lease termination by a total of $ 25 million. Under the terms of the new agreement, the Company reclassified these leases as finance leases.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. Commitments and Contingencies Litigation We are subject to certain legal actions which we consider routine to our business activities. As of December 31, 2023, our management believed the ultimate outcomes of other routine legal matters are not likely to have a material adverse effect on our financial position, liquidity or results of operations. Electric Aircraft Forward Purchase Commitments As described in Note 6, in February 2021, we entered into a forward purchase contract with Archer for a number of eVTOL aircraft. The aggregate base commitment for the eVTOL aircraft is $ 200.0 million, with an option to purchase additional aircraft. Our obligation to purchase the eVTOL aircraft is subject to the Company and Archer first agreeing in the future to a number of terms and conditions, which may or may not be met. As described in Note 6, in July 2021, we entered into a forward purchase contract with Heart for a number of fully electric aircraft. The maximum aggregate base commitment for the aircraft is $ 1,200.0 million, with an option to purchase additional aircraft. Our obligation to purchase the aircraft is subject to the Company and Heart first agreeing in the future to a number of terms and conditions, which may or may not be met. Other Commitments 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.

Subsequent Events

Subsequent Events	3 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events United Agreements On January 11, 2024 and January 19, 2024, we entered into the First Amendment to our Third Amended and Restated United CPA and the Second Amendment to our Third Amended and Restated United CPA (the "January 2024 United CPA Amendments"), respectively. The January 2024 United CPA Amendments provide additional liquidity and certain other amendments described below o Increased CPA rates, retroactive to October 1, 2023 through December 31, 2024. We generated an additional approximately $ 20.4 million in incremental revenue from October 1, 2023 through April 30, 2024, and are projected to generate an additional $ 26.8 million in incremental revenue from May 1, 2024 through December 31, 2024. • Amended certain notice requirements for removal by United of up to eight CRJ-900 Covered Aircraft (as defined in the United CPA) from the United CPA. • Extended United's existing utilization waiver for the Company's operation of E-175 and CRJ-900 Covered Aircraft (as defined in the United CPA) to June 30, 2024. On January 11, 2024 and January 19, 2024, we entered into Amendment No. 4 to our Second Amended and Restated Credit and Guaranty Agreement, Amendment No. 1 to Stock Pledge Agreement and Limited Waiver of Conditions to Credit Extension ("Amendment No. 4") and Waiver and Amendment No. 5 to our Second Amended and Restated Credit and Guaranty Agreement (collectively, the "January 2024 Credit Agreement Amendments"), respectively. The January 2024 Credit Agreement Amendments provide for the following: • The repayment in full of the Company's $ 10.5 million Effective Date Bridge Loan obligations, and the prepayment (and corresponding reduction) of approximately $ 2.1 million in Revolving Loans (as defined therein), with the proceeds from the sale, assignment, or transfer of the Company's vested investment in Heart Aerospace Incorporated. Subsequent to December 31, 2023, the Company transferred its vested investment in Heart Aerospace Incorporated to United and realized a gain on the investment of $ 7.2 million. • As a result of the repayment of the Effective Date Bridge Loan and pay down of the Revolving Loans, the shares of capital stock of Archer Aviation, Inc. held by the Company are being released as collateral for the United credit facility, subject to certain conditions. Additionally, as a result of the repayment of the Effective Date Bridge Loan, $ 10.5 million of the potential $ 15 million deemed prepayment was achieved and recognized as prepaid. • The waiver of certain financial covenant defaults with respect to the fiscal quarters ended June 30, 2023, September 30, 2023, and December 31, 2023 and the waiver of projected financial covenant defaults with respect to the fiscal quarter ending March 31, 2024. • An increase in the Applicable Margin (as defined in the United credit facility) during a specified period of time for borrowings under the Credit Agreement. • Loan prepayment requirements in connection with the sale of four specified aircraft engines and the addition of such engines as collateral for the United credit facility for a specified period of time. On May 8, 2024, we entered into a Waiver Agreement to our Second Amended and Restated Credit and Guaranty Agreement providing for the waiver of a certain projected financial covenant default with respect to the fiscal quarter ending June 30, 2024. On February 29, 2024, March 29, 2024, April 1, 2024, and April 19, 2024, and April 30, 2024, we received individual notices from United exercising its right under Section 2.4(a) of the United CPA to remove a total of 10 CRJ-900 Covered Aircraft (as defined in the United CPA), effective as follows: two aircraft - March 31, 2024; two aircraft - April 30, 2024; one aircraft - May 21, 2024; one aircraft - May 31, 2024; two aircraft June 30, 2024; and two aircraft - July 31, 2024. DHL Amendment In February 2024, we mutually agreed to the consensual wind-down of our flight operations on behalf of DHL and ceased all such operations on March 1, 2024. Engine Purchase Agreement Subsequent to December 31, 2023, we closed the sale of all 12 engines as part of the engine purchase agreement with a third party for gross proceeds of $ 54.2 million and $ 15.9 million of net proceeds after the retirement of debt. RASPRO Letter Agreement and Memorandum On April 15, 2024, the Company entered into a letter agreement with RASPRO to defer the $ 50.3 million buyout obligation until May 15, 2024, subject to the payment of additional sums by April 15, 2024 and April 29, 2024 and certain other conditions. On April 22, 2024, the Company entered into a binding Memorandum that provides for the payment of certain commitment fee amounts by the Company, which are due in May, July, and August, along with certain RASPRO Trust administration fee amounts, in consideration for the deferral of the buyout obligation until September 2024. Certain of the commitment fee amounts and Trust fees otherwise payable will be waived if the Company completes its purchase obligations with respect to all 15 airframes and 30 engines as set forth in the Memorandum. The terms agreed to in the Memorandum will be set forth in a definitive lease amendment to be entered into by the parties.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	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 GAAP 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. 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, 2023 included in the Company's Annual Report on Form 10-K for the year ended September 30, 2023 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.
Segment Reporting	Segment Reporting As of December 31, 2023 , our chief operating decision maker was the Chief Executive Officer. While we operate under a capacity purchase agreement and a flight services agreement, 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 and allocate resources, 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	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 Revenue	Contract Revenue and Pass-through and Other Revenue We recognize contract revenue when the service is provided under our CPA and FSA. Under the CPA and FSA, our major partners generally pay for each departure, flight hour or block hour incurred, and an amount per aircraft in service each month with additional incentives or penalties based on flight completion, on-time performance, and other operating metrics. Our performance obligation is met as each flight is completed, and revenue is recognized and reflected in contract revenue. We recognize pass-through revenue when the service is provided under our CPA and FSA. Pass-through revenue represents reimbursements for certain direct expenses incurred including passenger liability and hull insurance, property taxes, other direct costs defined within the agreements, and major maintenance on aircraft leased from our major partners at nominal rates. Our 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. We record deferred revenue when cash payments are received or are due from our major partners in advance of our performance. During the three months ended December 31, 2023, we recognized approximately $ 3.0 million of previously deferred revenue. Deferred revenue is recognized as flights are completed over the remaining terms of the respective contracts. The deferred revenue balance as of December 31, 2023 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 December 31, Total Deferred Revenue 2024 (remainder of) $ 2,139 2025 5,733 2026 4,350 2027 4,093 2028 1,625 Thereafter 105 Total $ 18,045 A portion of our compensation under our CPA with United is designed to reimburse the Company for certain aircraft ownership costs. Such costs include aircraft principal and interest debt service costs, aircraft depreciation, and interest expense or aircraft lease expense costs while the aircraft is under contract. We have concluded this component of the compensation under these agreements is lease revenue, as such agreements identify the "right of use" of a specific type and number of aircraft over a stated period of time. We account for the non-lease component under ASC 606 and account for the lease component under ASC 842. We allocate the consideration in the contract between the lease and non-lease components based on their stated contract prices, which is based on a cost basis approach representing our estimate of the stand-alone selling prices. The lease revenue associated with our CPA is accounted for as an operating lease and is reflected as contract revenue in the condensed consolidated statements of operations and comprehensive loss. We recognized $ 34.9 million and $ 41.1 million of lease revenue for the three months ended December 31, 2023 and December 31, 2022, respectively. We have not separately stated aircraft rental income in the condensed consolidated statements of operations and comprehensive loss because the use of the aircraft is not a separate activity from the total service provided under our CPA. Historically, the Company had lease agreements with GoJet Airlines LLC (“GoJet”) to lease 20 CRJ-700 aircraft. The lease agreements are accounted for as operating leases and have a term of nine ( 9 ) years beginning on the delivery date of each aircraft. 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 contract revenue. Lease revenue for supplemental rent is deferred and recognized within contract revenue when it is probable that amounts received will not be reimbursed for future qualifying maintenance events over the lease term. The Company mitigated 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 leases have specified lease return condition requirements and we maintain inspection rights under the leases. Lease incentive obligations for reimbursements of certain aircraft maintenance costs are recognized as lease incentive assets and were amortized on a straight-line basis and recognized as a reduction to lease revenue over the lease term. During fiscal year 2022, the Company terminated its lease agreements with GoJet to lease 18 of the 20 CRJ-700 aircraft and classified the 18 aircraft as assets held for sale. All 18 aircraft were sold as of December 31, 2023. The remaining two lease agreements are accounted for as finance leases. The following table summarizes future minimum rental payments under operating leases related to leased aircraft that had remaining non-cancelable lease terms as of December 31, 2023 (in thousands): Periods Ending December 31, Total Payments 2024 (remainder of) $ 1,638 2025 2,184 2026 2,184 2027 2,184 2028 2,184 Thereafter 5,824 Total $ 16,198
Leases	Leases We determine if an arrangement is a lease at inception. As a lessee, we have lease agreements with lease and non-lease components and have elected to account for such components as a single lease component. Our operating lease activities are recorded in operating lease right-of-use assets, current maturities of operating leases, and noncurrent operating lease liabilities in the condensed consolidated balance sheets. Finance leases are reflected in property and equipment, net, current portion of long-term debt and finance leases, and long-term debt and finance leases, excluding current portion in the condensed consolidated balance sheets. Right-of-use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. Certain variable lease payments are not included in the calculation of the right-of-use assets and lease liability due to uncertainty of the payment amount and are recorded as lease expense in the period incurred. In determining the present value of lease payments, we use either the implicit rate in the lease when it is readily determinable or our estimated incremental borrowing rate, based on information available at the lease commencement. Our lease terms include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Operating lease costs are recognized on a straight-line basis over the lease term, while finance leases result in a front-loaded expense pattern. As a lessee, we have elected a short-term lease practical expedient on all classes of underlying assets, permitting us to not apply the recognition requirements of ASC 842 to leases with terms of 12 months or less. We lease, at nominal rates, certain aircraft from United and DHL under our CPA and FSA, which are excluded from operating lease assets and liabilities as they do not represent embedded leases under ASC 842. Other than such leases at nominal amounts, 18 of our aircraft are leased from third parties. In the event that we or one of our major 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 are written off.
Contract Liabilities	Contract Liabilities Contract liabilities consist of deferred credits for cost reimbursements from major partners related to aircraft modifications and pilot training associated with the capacity purchase agreement. The deferred credits are recognized over time depicting the pattern of the transfer of control of services resulting in ratable recognition of revenue over the remaining term of the capacity purchase agreement. Current and non-current deferred credits are recorded in other accrued expenses and non-current deferred credits in the condensed consolidated balance sheets. Our total current and non-current deferred credit balances at December 31, 2023 and September 30, 2023 were $ 4.9 million and $ 5.1 million, respectively. We recognized $ 1.0 million and $ 0.2 million of the deferred credits within contract revenue during the three months ended December 31, 2023 and December 31, 2022 , respectively.
Maintenance Expense	Maintenance Expense We operate 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. We account 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 $ 0.8 million and $ 0.8 million for the three months ended December 31, 2023 and December 31, 2022, respectively. As of December 31, 2023 and September 30, 2023, our deferred heavy maintenance balance, net of accumulated amortization, was $ 7.2 million and $ 8.0 million, respectively. We account for heavy maintenance and major overhaul costs for all other fleets under the direct expense method whereby 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 $ 5.8 million and $ 8.7 million for the three months ended December 31, 2023 and December 31, 2022, respectively, of which $ 5.7 million and $ 8.7 million, respectively, was pass-through expense. Airframe C-check expense totaled $ 6.4 million and $ 5.1 million for the three months ended December 31, 2023 and December 31, 2022, respectively, of which $ 3.8 million and $ 4.4 million, respectively, was pass-through expense.
Assets Held for Sale	Assets Held for Sale We classify assets as held for sale when our management approves and commits to a formal plan of sale that is probable of being completed within one year. Assets designated as held for sale are recorded at the lower of their current carrying value or their fair market value, less costs to sell, beginning in the period in which the assets meet the criteria to be classified as held for sale. See Note 5 for further discussion of our assets classified as held for sale as of December 31, 2023 .

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Schedule of Deffered Revenue Remaining Performance Obligations	Periods Ending December 31, Total Deferred Revenue 2024 (remainder of) $ 2,139 2025 5,733 2026 4,350 2027 4,093 2028 1,625 Thereafter 105 Total $ 18,045
Schedule of Future Minimum Rental Payments under Non-cancelable Operating Leases	Periods Ending December 31, Total Payments 2024 (remainder of) $ 1,638 2025 2,184 2026 2,184 2027 2,184 2028 2,184 Thereafter 5,824 Total $ 16,198

Assets Held for Sale (Tables)

Assets Held for Sale (Tables)	3 Months Ended
	Dec. 31, 2023
Discontinued Operations and Disposal Groups [Abstract]
Summarizes Company's Held for Sale Activity	The following table summarizes the Company's held for sale activity during the three months ended December 31, 2023 (in millions): Total Current Assets Noncurrent Assets Held for sale balance as of September 30, 2023 $ 69.7 $ 57.7 $ 12.0 Assets sold ( 53.9 ) ( 41.9 ) ( 12.0 ) Assets reclassified to held for sale 111.7 71.4 40.3 Impairment gain due to fair value adjustments 5.1 5.1 — Held for sale balance as of December 31, 2023 $ 132.6 $ 92.3 $ 40.3

Balance Sheet Information (Tabl

Balance Sheet Information (Tables)	3 Months Ended
	Dec. 31, 2023
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 condensed consolidated balance sheets consisted of the following (in thousands): December 31, September 30, 2023 2023 Expendable parts and supplies, net: Expendable parts and supplies $ 40,215 $ 39,630 Less: expendable parts warranty ( 7,218 ) ( 6,295 ) Less: obsolescence ( 4,167 ) ( 4,090 ) $ 28,830 $ 29,245 Prepaid expenses and other current assets: Prepaid aviation insurance $ 1,596 $ 3,176 Prepaid vendors 896 143 Prepaid other insurance 761 1,205 Lease incentives 143 1,125 Prepaid fuel and other 1,080 1,645 $ 4,476 $ 7,294 Property and equipment, net: Aircraft and other flight equipment $ 779,436 $ 1,039,782 Other equipment 9,467 9,421 Total property and equipment 788,903 1,049,203 Less: accumulated depreciation ( 254,444 ) ( 351,181 ) $ 534,459 $ 698,022 Other assets: Investments in equity securities $ 23,021 $ 20,320 Lease incentives 919 954 Contract asset 8,309 8,756 Other 515 516 $ 32,764 $ 30,546 Other accrued expenses: Accrued property taxes $ 3,052 $ 5,281 Accrued interest 5,099 3,447 Accrued vacation 6,933 6,763 Accrued lodging 3,165 3,984 Accrued maintenance 1,546 2,117 Accrued simulator costs 242 1,006 Accrued employee benefits 1,681 1,450 Accrued fleet operating expense 1,668 650 Other 4,388 2,303 $ 27,774 $ 27,001 Other noncurrent liabilities: Warrant liabilities $ 25,225 $ 25,225 Lease incentive obligations 1,050 1,050 Long-term employee benefits 495 429 Other 1,819 1,818 $ 28,589 $ 28,522

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Carrying Value and Estimated Fair Value of Long-term Debt and Finance Leases, Including Current Maturities	The carrying value and estimated fair value of our total long-term debt and finance leases, including current maturities, were as follows (in millions): December 31, 2023 September 30, 2023 Carrying Fair Carrying Fair Value Value Value Value Long-term debt and finance leases, including current maturities (1) $ 481.0 $ 456.0 $ 538.3 $ 493.6 (1) Current and prior period long-term debts' carrying and fair values exclude net debt issuance costs.

Long-Term Debt, Finance Lease_2

Long-Term Debt, Finance Leases, and Other Borrowings (Tables)	3 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Long-term Debt	Long-term debt as of December 31, 2023 and September 30, 2023, consisted of the following (in thousands): December 31, September 30, 2023 2023 Senior and subordinated notes payable to secured parties, due in monthly installments, interest based on SOFR plus interest spread at 2.71 % through 2027 , collateralized by the underlying aircraft $ - $ 39,018 Notes payable to secured parties, due in semi-annual installments, interest based on SOFR plus interest spread at 4.75 % to 6.25 % through 2028 , collateralized by the underlying aircraft 108,815 108,815 Notes payable to secured parties, due in quarterly installments, interest based on SOFR plus interest at spread 2.20 % to 2.32 % for senior note & 4.50 % for subordinated note through 2028 , collateralized by the underlying aircraft 86,194 90,401 Revolving credit facility, quarterly interest based on SOFR plus interest spread at 4.50 % through 2028 , with incentives for up to $ 15 million based on achieving certain performance metrics 45,630 40,630 United Bridge Loan - due in quarterly installments based on SOFR plus interest spread at 4.50 % through 2024 10,500 10,500 Other obligations due to financial institution, monthly and/or quarterly interest due from 2022 through 2031 , collateralized by the underlying equipment 68,540 67,637 Notes payable to financial institution, due in monthly installments, interest based on SOFR plus interest spread at 3.10 % through 2024 , collateralized by the underlying equipment 271 1,075 Notes payable to financial institution, due in monthly installments, interest based on fixed interest of 7.50 %, through 2024 , collateralized by the underlying equipment 38,846 41,098 Notes payable to financial institution, quarterly interest based on SOFR plus interest spread at 3.50 % through 2027 122,155 139,100 Gross long-term debt, including current maturities 480,951 538,274 Less unamortized debt issuance costs ( 4,383 ) ( 5,083 ) Less notes payable warrants ( 4,315 ) ( 4,913 ) Net long-term debt, including current maturities 472,253 528,278 Less current portion, net of unamortized debt issuance costs ( 156,789 ) ( 163,550 ) Net long-term debt $ 315,464 $ 364,728
Schedule of Principal Maturities of Long-term Debt	Principal maturities of long-term debt as of December 31, 2023, and for each of the next five years are as follows (in thousands): Periods Ending December 31, Total Principal 2024 (remainder of) $ 152,275 2025 49,263 2026 172,700 2027 51,313 2028 30,878 Thereafter 24,522 $ 480,951

Loss Per Share (Tables)

Loss Per Share (Tables)	3 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Calculations of Net Loss Per Common Share	Calculations of net loss per common share were as follows (in thousands): Three Months Ended December 31, 2023 2022 Net loss $ ( 57,850 ) $ ( 9,090 ) Basic weighted average common shares outstanding 40,940 36,378 Diluted weighted average common shares outstanding 40,940 36,378 Net loss per common share attributable to Mesa Air Group: Basic $ ( 1.41 ) $ ( 0.25 ) Diluted $ ( 1.41 ) $ ( 0.25 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of Restricted Share Activity	The restricted share activity for the three months ended December 31, 2023 is summarized as follows: Weighted- Average Number Grant Date of Shares Fair Value Restricted shares unvested at September 30, 2023 736,891 $ 3.35 Granted — $ — Vested — $ — Forfeited ( 8,000 ) $ 4.72 Restricted shares unvested at December 31, 2023 728,891 $ 3.33

Leases (Tables)

Leases (Tables)	3 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Components of Lease Costs	The components of our lease costs were as follows (in thousands): Three Months Ended December 31, 2023 2022 Operating lease costs $ 1,278 $ 4,699 Variable and short-term lease costs 1,279 889 Interest expense on finance lease liabilities 1,289 274 Amortization expense of finance lease assets 4,123 1,046 Total lease costs $ 7,969 $ 6,907

Organization and Operations - A

Organization and Operations - Additional Information (Detail) $ in Thousands				1 Months Ended		3 Months Ended	7 Months Ended
	Jan. 11, 2024 USD ($) AirCraft	Jan. 01, 2024 USD ($) Engine	Dec. 01, 2023 Engine	Jan. 31, 2024 AirCraft	Dec. 31, 2023 USD ($) DailyDeparture AirCraft State	Dec. 31, 2023 USD ($) DailyDeparture AirCraft State Engine Employee City	Apr. 30, 2024 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of states in which entity operates | State					36	36
Additional payments received related to block hour rate increase						$ 8,800
Number of aircrafts operated | AirCraft						80
Number of cities in which entity operates | City						82
Number of daily departures | DailyDeparture					280	280
Number of employees | Employee						2,246
Long-term debt					$ 156,800	$ 156,800
Number of surplus engines to be sold | Engine			12
Loan forgiven						2,954
Reduction in loan amount						$ 5,000
Number of engines held to sale | Engine						48
Purchase agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Gross proceeds from sale of asset						$ 11,500
Number of engines held to sale | Engine						23
Impact of Pilot Shortage and Transition of Operations to United [Member] | Export Development Bank of Canada Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Principal contingent amount upon repayment						$ 4,200
Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated | AirCraft						15
Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional payments received related to block hour rate increase							$ 21,300
Number of aircraft sold	4	12
Gross proceeds from sale of asset		$ 54,200
Proceeds from sale of asset		15,900
Subsequent Event [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional revenue and liquidity	$ 20,400
Subsequent Event [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional revenue and liquidity	26,800
Revolving Credit Facility [Member] | Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Repayments of long term debt	2,100
United [Member] | Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Repayments of long term debt	10,500
United Capacity Purchase Agreement [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated | AirCraft						80
United Capacity Purchase Agreement [Member] | Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Realized and unrealized gain on investment		$ 7,200
Repayments of long term debt	10,500
United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional revenue and liquidity	20,400
United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Additional revenue and liquidity	$ 26,800
CRJ-900 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircraft sold | AirCraft						4
Number of aircraft to be sold | AirCraft						11
Gross proceeds from sale of asset						$ 12,000
CRJ-900 Aircraft [Member] | Edc Loan And Mhirj Junior Note
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Repayments of long term debt						4,200
Proceeds from sale of asset						600
Loan forgiven						$ 5,000
CRJ-900 Aircraft [Member] | American Airlines Inc [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircraft sold | AirCraft						4
Gross proceeds from sale of asset						$ 41,500
Proceeds from sale of asset						$ 5,700
CRJ-900 Aircraft [Member] | American Airlines Inc [Member] | Export Development Bank of Canada Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircraft sold | AirCraft						7
CRJ-900 Aircraft [Member] | United Capacity Purchase Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated | AirCraft					26	26
Maximum number of aircraft to be operated | AirCraft						38
CRJ-900 Aircraft [Member] | United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated | AirCraft				8
E-175 Aircraft [Member] | United Capacity Purchase Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated | AirCraft						54
E-175 Aircraft [Member] | United Capacity Purchase Agreement [Member] | United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated | AirCraft						42
Number of aircrafts owned | AirCraft						18
Lease expiration year						2028
Notice period for termination of agreement						United, subject to certain conditions, including the payment of certain costs tied to aircraft type, to terminate the agreement in its discretion, or remove aircraft from service, by giving us notice of 90 days or more
E-175 Aircraft [Member] | United Capacity Purchase Agreement [Member] | United [Member] | Minimum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Lease expiration year						2024
E-175 Aircraft [Member] | United Capacity Purchase Agreement [Member] | United [Member] | Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Lease expiration year						2028
E175LL Aircraft [Member] | United Capacity Purchase Agreement [Member] | United [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Notice period for termination of agreement						United, subject to certain conditions, including the payment of certain costs tied to aircraft type, may terminate the agreement in its discretion, or remove E-175 aircraft from service, by giving us notice of 90 days or more
UST Loan [Member] | CRJ-900 Aircraft [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircraft sold | AirCraft						4
Gross proceeds from sale of asset						$ 12,000
Proceeds from sale of asset						$ 6,500

Organization and Operations -_2

Organization and Operations - Additional Information (Detail1) $ in Thousands

1 Months Ended

3 Months Ended

Jul. 31, 2024 AirCraft

Jun. 30, 2024 AirCraft

May 31, 2024 AirCraft

May 21, 2024 AirCraft

Apr. 30, 2024 AirCraft

Apr. 22, 2024 AirCraft

Apr. 15, 2024 USD ($)

Mar. 31, 2024 AirCraft

Jan. 01, 2024 USD ($)

Jan. 13, 2023 shares

Sep. 30, 2024 USD ($)

Dec. 31, 2023 AirCraft shares

Aug. 31, 2022 AirCraft

Mar. 31, 2024 USD ($) AirCraft

Dec. 31, 2023 shares

Dec. 31, 2023 USD ($) shares

Dec. 31, 2023 AirCraft shares

Dec. 31, 2023 shares

Dec. 31, 2023 Engine shares

Dec. 31, 2023 Airframes shares

Dec. 31, 2022 USD ($)

Sep. 30, 2023 shares

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Net cash provided by operating activities

$ (7,841)

$ (6,034)

Net Income (Loss)

$ (57,850)

$ (9,090)

Number of spare engines classified as held for sale | Engine

48

Number of aircrafts operated | AirCraft

80

United capacity purchase agreement termination notice period

30 days

Consideration for amended description

Additionally, in January 2023, in consideration for entering in the Amended and Restated United CPA and providing the revolving line of credit, discussed in Note 8, the Company (i) granted United the right to designate one individual to the Company's board of directors (the "United Designee"), which occurred effective May 2, 2023 with the appointment of Jonathan Ireland and (ii) issued to United 4,042,061 shares of the Company’s common stock equal to approximately 10% of the Company’s issued and outstanding capital stock on such date (the "United Shares"). United's board designee rights will terminate at such time as United's equity ownership in the Company falls below five percent (5%) of the Company's issued and outstanding stock.

Common stock, shares issued | shares

40,940,326

40,940,326

40,940,326

40,940,326

40,940,326

40,940,326

40,940,326

40,940,326

United [Member] | United Capacity Purchase Agreement [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Common stock, shares issued | shares

4,042,061

Common stock issued equivalent percentage of issued and outstanding capital stock

10%

Impact of Pilot Shortage and Transition of Operations to United [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Percentage of increased hourly payment for captains

118%

Percentage of increased hourly payment for new hires

172%

Net cash provided by operating activities

$ 7,800

Net Income (Loss)

57,900

Non-cash impairment charge

40,400

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Letter Agreement [Member] | Forecast [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Buyout price

$ 50,300

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Binding Memorandum [Member] | Subsequent Event [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Buyout price

$ 50,300

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Number of aircrafts operated | AirCraft

15

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement [Member] | Forecast [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Net cash from aircraft and equipment purchase agreement

$ (12,100)

Buyout price

$ 50,300

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement One [Member] | Forecast [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Number of engines | AirCraft

30

30

Buyout pricing

$ 19,500

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement Two [Member] | Forecast [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Number of airframes without engines | AirCraft

15

15

Buyout pricing

$ 18,800

CRJ-900 Aircraft [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Non-cash impairment charge

$ 40,400

Number of aircraft classified as assets held for sale | AirCraft

11

Number of airframes without engines

11

11

Number of aircraft to be removed | AirCraft

10

CRJ-900 Aircraft [Member] | United Capacity Purchase Agreement [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Number of aircrafts operated | AirCraft

26

26

CRJ-900 Aircraft [Member] | Forecast [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Number of aircraft to be removed | AirCraft

2

2

1

1

2

2

CRJ-700 Aircraft [Member] | United [Member] | United Capacity Purchase Agreement [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Aircraft lease term

9 years

Number of aircrafts listed for sale | AirCraft

18

Number of aircraft lease terminated | AirCraft

18

E175LL Aircraft [Member] | United [Member] | United Capacity Purchase Agreement [Member]

Organization Consolidation And Presentation Of Financial Statements [Line Items]

Notice period for termination of agreement

United, subject to certain conditions, including the payment of certain costs tied to aircraft type, may terminate the agreement in its discretion, or remove E-175 aircraft from service, by giving us notice of 90 days or more

Organization and Operations -_3

Organization and Operations - Additional Information (Detail2) - AirCraft		3 Months Ended
	Dec. 20, 2019	Dec. 31, 2023
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated		80
Boeing 737-400F [Member] | DHL Flight Services Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircrafts operated	4
Number of aircraft leased	2
Aircraft lease term	5 years
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.
Notice period for termination of agreement		At any time after the first anniversary of the commencement date of the first aircraft placed in service with 90 days' written notice.
Boeing 737-800F [Member] | DHL Flight Services Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of aircraft leased	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions			3 Months Ended		12 Months Ended
	Jan. 11, 2024 AirCraft	Jan. 01, 2024 Engine	Dec. 31, 2023 USD ($) AirCraft	Dec. 31, 2022 USD ($)	Sep. 30, 2022 AirCraft	Sep. 30, 2023 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue			$ 3
Lease revenue			$ 34.9	$ 41.1
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]			Revenue From Contract With Customer Excluding Assessed Tax	Revenue From Contract With Customer Excluding Assessed Tax
Number of air craft leased from third parties | AirCraft			18
Current and non-current deferred credit contract liability balances			$ 4.9			$ 5.1
Recognized deferred credits within contract revenue			1	$ 0.2
Amortization of heavy maintenance and major overhaul costs charged to depreciation and amortization expense			0.8	0.8
Deferred heavy maintenance balance, net of accumulated amortization			7.2			$ 8
Engine overhaul expense			5.8	8.7
Engine overhaul pass-through expense			5.7	8.7
Airframe check expense			6.4	5.1
Airframe check pass-through expense			$ 3.8	$ 4.4
CRJ 700 [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft to be leased | AirCraft			20		20
Operating lease, term of contract			9 years
CRJ 700 [Member] | GoJet Agreements [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft classified as assets held for sale | AirCraft					18
Number of aircraft sold | AirCraft			18
Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of aircraft sold	4	12

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Deferred Revenue Remaining Performance Obligations (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 18,045
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 2,139
Deferred Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 5,733
Deferred Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 4,350
Deferred Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 4,093
Deferred Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 1,625
Deferred Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2028-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Deferred Revenue	$ 105
Deferred Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Deferred Revenue Remaining Performance Obligations (Detail 1) $ in Thousands	Dec. 31, 2023 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Deferred Revenue	$ 18,045

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Future Minimum Rental Payments under Non-cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
2024 (remainder of)	$ 1,638
2025	2,184
2026	2,184
2027	2,184
2028	2,184
Thereafter	5,824
Total	$ 16,198

Concentrations of Credit Risk -

Concentrations of Credit Risk - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Concentration Risk [Line Items]
Restricted cash	$ 3,134,000		$ 3,132,000
Outstanding letters of credit to be collateralized by amounts on deposit	3,100,000
Allowance for doubtful accounts	$ 0		$ 0
Sales Revenue, Net [Member] | American Airlines Inc. [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	0%	45%
Sales Revenue, Net [Member] | United [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	96%	50%

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Impairment loss on intangible assets	$ 40,384	$ 3,719

Assets Held for Sale - Addition

Assets Held for Sale - Additional Information (Detail) $ in Thousands				3 Months Ended					12 Months Ended
	Jan. 11, 2024 AirCraft	Jan. 01, 2024 USD ($) Engine	Dec. 01, 2023 Engine	Dec. 31, 2023 USD ($) AirCraft	Dec. 31, 2023 USD ($) AirCraft	Dec. 31, 2023 USD ($) AirCraft Engine	Dec. 31, 2023 USD ($) AirCraft Airframes	Dec. 31, 2022 USD ($)	Sep. 30, 2023 USD ($) AirCraft
Long Lived Assets Held For Sale [Line Items]
Asset impairment				$ 40,384				$ 3,719
Assets held for sale				40,336	$ 40,336	$ 40,336	$ 40,336		$ 12,000
Number of surplus engines to be sold | Engine			12
Number of engines held to sale | Engine						48
Proceeds from sale of aircraft and engines				53,489
Current Assets [Member]
Long Lived Assets Held For Sale [Line Items]
Assets held for sale				92,300	92,300	$ 92,300	92,300		57,700
Noncurrent Assets [Member]
Long Lived Assets Held For Sale [Line Items]
Assets held for sale				40,300	$ 40,300	$ 40,300	$ 40,300		$ 12,000
Subsequent Event [Member]
Long Lived Assets Held For Sale [Line Items]
Gross proceeds from sale of asset		$ 54,200
Proceeds from sale of asset		$ 15,900
Number of aircraft sold	4	12
CRJ-900 Aircraft [Member]
Long Lived Assets Held For Sale [Line Items]
Asset impairment				45,500
Impairment loss related to the held for sale aircraft				$ 40,400
Number of aircraft held for sale | AirCraft					8				15
Number of aircrafts held for sale | AirCraft				15	15	15	15
Gross proceeds from sale of asset				$ 12,000
Assets held for sale				132,600	$ 132,600	$ 132,600	$ 132,600		$ 69,700
Assets sold held for sale				53,900
Assets reclassified to held for sale				111,700
Impairment gain due to fair value adjustments				5,100
Number of aircraft sold | AirCraft					4
Number of airframes without engines					11		11
CRJ-900 Aircraft [Member] | Current Assets [Member]
Long Lived Assets Held For Sale [Line Items]
Assets held for sale				92,300	$ 92,300	92,300	$ 92,300		57,700
Assets sold held for sale				41,900
Assets reclassified to held for sale				71,400
Impairment gain due to fair value adjustments				5,100
CRJ-900 Aircraft [Member] | Noncurrent Assets [Member]
Long Lived Assets Held For Sale [Line Items]
Assets held for sale				40,300	$ 40,300	$ 40,300	$ 40,300		$ 12,000
Assets sold held for sale				12,000
Assets reclassified to held for sale				40,300
CRJ-900 Aircraft [Member] | UST Loan [Member]
Long Lived Assets Held For Sale [Line Items]
Gross proceeds from sale of asset				12,000
Proceeds from sale of asset				6,500
Number of aircraft sold | AirCraft					4
CF34-8C Aircraft [Member]
Long Lived Assets Held For Sale [Line Items]
Number of surplus engines to be sold | Engine						48
American Airlines Inc. [Member] | CRJ-900 Aircraft [Member]
Long Lived Assets Held For Sale [Line Items]
Gross proceeds from sale of asset				41,500
Proceeds from sale of asset				$ 5,700
Number of aircraft sold | AirCraft					4

Assets Held for Sale - Summariz

Assets Held for Sale - Summarizes Company's Held for Sale Activity (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2023 USD ($)
Long-Lived Assets Held-for-Sale [Line Items]
Assets held for sale, Beginning balance	$ 12,000
Assets held for sale, Ending balance	40,336
Current Assets [Member]
Long-Lived Assets Held-for-Sale [Line Items]
Assets held for sale, Beginning balance	57,700
Assets held for sale, Ending balance	92,300
Noncurrent Assets [Member]
Long-Lived Assets Held-for-Sale [Line Items]
Assets held for sale, Beginning balance	12,000
Assets held for sale, Ending balance	40,300
CRJ-900 Aircraft [Member]
Long-Lived Assets Held-for-Sale [Line Items]
Assets held for sale, Beginning balance	69,700
Assets sold	(53,900)
Assets reclassified to held for sale	111,700
Impairment gain due to fair value adjustments	5,100
Assets held for sale, Ending balance	132,600
CRJ-900 Aircraft [Member] | Current Assets [Member]
Long-Lived Assets Held-for-Sale [Line Items]
Assets held for sale, Beginning balance	57,700
Assets sold	(41,900)
Assets reclassified to held for sale	71,400
Impairment gain due to fair value adjustments	5,100
Assets held for sale, Ending balance	92,300
CRJ-900 Aircraft [Member] | Noncurrent Assets [Member]
Long-Lived Assets Held-for-Sale [Line Items]
Assets held for sale, Beginning balance	12,000
Assets sold	(12,000)
Assets reclassified to held for sale	40,300
Assets held for sale, Ending balance	$ 40,300

Balance Sheet Information - Sum

Balance Sheet Information - Summary of Certain Significant Amounts Included in Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Expendable parts and supplies, net:
Expendable parts and supplies	$ 40,215	$ 39,630
Less: expendable parts warranty	(7,218)	(6,295)
Less: obsolescence	(4,167)	(4,090)
Expendable parts and supplies, net	28,830	29,245
Prepaid expenses and other current assets:
Prepaid aviation insurance	1,596	3,176
Prepaid vendors	896	143
Prepaid other insurance	761	1,205
Lease incentives	143	1,125
Prepaid fuel and other	1,080	1,645
Prepaid expenses and other current assets	4,476	7,294
Property and equipment, net:
Property and equipment-gross	788,903	1,049,203
Less: accumulated depreciation	(254,444)	(351,181)
Property and equipment-net	534,459	698,022
Other assets:
Investments in equity securities	23,021	20,320
Lease incentives	919	954
Contract asset	8,309	8,756
Other	515	516
Other assets	32,764	30,546
Other accrued expenses:
Accrued property taxes	3,052	5,281
Accrued interest	5,099	3,447
Accrued vacation	6,933	6,763
Accrued lodging	3,165	3,984
Accrued maintenance	1,546	2,117
Accrued simulator costs	242	1,006
Accrued employee benefits	1,681	1,450
Accrued fleet operating expense	1,668	650
Other	4,388	2,303
Other accrued expenses	27,774	27,001
Other noncurrent liabilities:
Warrant liabilities	25,225	25,225
Lease incentive obligations	1,050	1,050
Long-term employee benefits	495	429
Other	1,819	1,818
Other noncurrent liabilities	28,589	28,522
Aircraft and Other Flight Equipment [Member]
Property and equipment, net:
Property and equipment-gross	779,436	1,039,782
Other Machinery and Equipment [Member]
Property and equipment, net:
Property and equipment-gross	$ 9,467	$ 9,421

Balance Sheet Information - Add

Balance Sheet Information - Additional Information (Detail) $ in Thousands			1 Months Ended		3 Months Ended		12 Months Ended
	Jan. 01, 2024 USD ($)	Dec. 01, 2023 Engine	Sep. 30, 2021 USD ($) shares	Jul. 31, 2021 USD ($)	Dec. 31, 2023 USD ($) Airframes Engine	Dec. 31, 2022 USD ($)	Sep. 30, 2023 USD ($) AirCraft	Feb. 28, 2022 USD ($)	Feb. 28, 2021 USD ($)
Condensed Balance Sheet Statements Captions [Line Items]
Number of surplus engines to be sold | Engine		12
Depreciation expense					$ 13,300	$ 14,400
Estimated initial equity warrant asset value									$ 16,400
Investments in equity securities					23,021		$ 20,320
Estimated initial warrant asset value								$ 3,200
Net gain/(loss) on investments in equity securities					2,500	(1,700)
Aggregate carrying amount of investments in equity securities					23,000		20,300
Investments without readily determinable fair value					8,800		$ 8,800
Asset impairment					40,384	$ 3,719
Subsequent Event [Member] | United Capacity Purchase Agreement [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Realized and unrealized gain on investment	$ 7,200
Archer Aviation, Inc. [Member] | Level 1 [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Realized and unrealized gain on investment					2,500
Investments in equity securities					$ 13,900
Heart Aerospace Incorporated [Member] | Forward Purchase Contract [Member] | Preferred Stock [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Purchase of preferred stock				$ 5,000
Initial investment in preferred stock measured at cost				$ 5,000
Class A [Member] | Archer Aviation, Inc. [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Stock issued during period, Shares | shares			500,000
Stock issued during period, Value			$ 5,000
Total grant date value, Additional warrant to purchase shares			$ 5,600
CRJ-900 [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Number of aircraft held for sale | AirCraft							8
Number of Airframes without Engines | Airframes					11
CRJ-900 [Member] | RASPRO and Export Development Canada Aircraft Lease Agreement [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Impairment loss related to the held for sale aircraft					$ 40,400
CF34-8C Aircraft [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Number of surplus engines to be sold | Engine					48

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Value and Estimated Fair Value of Long-term Debt and Finance Leases, Including Current Maturities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Long-term debt and finance leases, including current maturities, carrying value	$ 480,951	$ 538,274
Long-term debt and finance leases, including current maturities, fair value	$ 456,000	$ 493,600

Long-Term Debt, Finance Lease_3

Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Long-term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 480,951	$ 538,274
Less unamortized debt issuance costs	(4,383)	(5,083)
Less notes payable warrants	(4,315)	(4,913)
Net long-term debt, including current maturities	472,253	528,278
Less current portion, net of unamortized debt issuance costs	(156,789)	(163,550)
Net long-term debt	315,464	364,728
Revolving credit facility quaterly collateralized by underlying equipment and investments through two thousand twenty eight [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	45,630	40,630
Senior and Subordinated Notes Payable to Secured Parties, Due in Monthly Installments Collateralized by the Underlying Aircraft Through 2027 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities		39,018
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	108,815	108,815
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	86,194	90,401
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	10,500	10,500
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	68,540	67,637
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2024 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	271	1,075
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2024 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	38,846	41,098
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member]
Debt Instrument [Line Items]
Gross long-term debt, including current maturities	$ 122,155	$ 139,100

Long-Term Debt, Finance Lease_4

Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Long-term Debt (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023
Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2028	2028
Long term debt interest rate description	quarterly interest based on SOFR plus interest spread at 4.50%
Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	4.50%
Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member] | Maximum [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Incentive recieved	$ 15
Senior and Subordinated Notes Payable to Secured Parties, Due in Monthly Installments Collateralized by the Underlying Aircraft Through 2027 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2027	2027
Long term debt interest rate description	due in monthly installments, interest based on SOFR plus interest spread at 2.71%
Senior and Subordinated Notes Payable to Secured Parties, Due in Monthly Installments Collateralized by the Underlying Aircraft Through 2027 [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	2.71%
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2028	2028
Long term debt interest rate description	due in semi-annual installments, interest based on SOFR plus interest spread at 4.75% to 6.25%
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member] | Minimum [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	4.75%
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member] | Maximum [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	6.25%
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2028	2028
Long term debt interest rate description	due in quarterly installments, interest based on SOFR plus interest at spread 2.20% to 2.32% for senior note & 4.50% for subordinated note
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member] | Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	4.50%
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member] | Minimum [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	2.20%
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member] | Maximum [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	2.32%
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2024 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2024	2024
Long term debt interest rate description	due in monthly installments, interest based on fixed interest of 7.50%, through 2024
Long term debt, basis spread on variable rate	7.50%
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member]
Debt Instrument [Line Items]
Long term debt interest rate description	monthly and/or quarterly interest due from 2022 through 2031
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2022
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2031	2031
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2027	2027
Long term debt interest rate description	Notes payable to financial institution, quarterly interest based on SOFR plus interest spread at 3.50%
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	3.50%
Notes Payable To Financial Institution Due In Monthly Installments Collateralized By Underlying Equipment Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2024	2024
Long term debt interest rate description	due in monthly installments, interest based on SOFR plus interest spread at 3.10%
Notes Payable To Financial Institution Due In Monthly Installments Collateralized By Underlying Equipment Through Two Thousand Twenty Four [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	3.10%
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Long term debt interest rate description	due in quarterly installments based on SOFR plus interest spread at 4.50%
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2024	2024
Long term debt, basis spread on variable rate	4.50%

Long-Term Debt, Finance Lease_5

Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Principal Maturities of Long-term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Long-Term Debt, Fiscal Year Maturity [Abstract]
2024 (remainder of)	$ 152,275
2025	49,263
2026	172,700
2027	51,313
2028	30,878
Thereafter	24,522
Long-term debt	$ 480,951	$ 538,274

Long-Term Debt, Finance Lease_6

Long-Term Debt, Finance Leases, and Other Borrowings - Additional Information (Detail)

1 Months Ended

3 Months Ended

9 Months Ended

Jan. 11, 2024 USD ($)

Jan. 01, 2024 USD ($)

Sep. 06, 2023 USD ($)

Dec. 27, 2022 USD ($)

Oct. 30, 2020 USD ($) $ / shares shares

Dec. 31, 2021 USD ($)

Dec. 31, 2023 USD ($) $ / shares

Jun. 30, 2023 USD ($)

May 23, 2024 USD ($)

Sep. 30, 2023 USD ($)

Dec. 31, 2022

Dec. 31, 2020 USD ($)

Debt Instrument [Line Items]

Property and equipment-gross

$ 788,903,000

$ 1,049,203,000

Long-Term Debt

$ 472,253,000

$ 528,278,000

Warrants of common stock exercise price | $ / shares

$ 3.98

Treasury Loan [Member] | Maximum [Member]

Debt Instrument [Line Items]

Calculated collateral coverage ratio

1.55

Treasury Loan [Member] | Minimum [Member]

Debt Instrument [Line Items]

Additional collateral coverage ratio

1.55

Loan Agreement [Member]

Debt Instrument [Line Items]

Warrants to purchase shares of common stock | shares

4,899,497

Warrants of common stock exercise price | $ / shares

$ 3.98

Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Permitted amount to redraw from existing credit facility

$ 7,900,000

Revolving Credit Facility [Member] | Subsequent Event [Member]

Debt Instrument [Line Items]

Repayments of long term debt

$ 2,100,000

Line of credit available to draw

$ 2,200,000

Revolving Credit Facility [Member] | Maximum [Member]

Debt Instrument [Line Items]

Revolving commitments

50,700,000

Revolving Credit Facility [Member] | Minimum [Member]

Debt Instrument [Line Items]

Revolving commitments

$ 30,700,000

Spare Engine Facility [Member] | Loan Agreement [Member]

Debt Instrument [Line Items]

Debt instrument, face amount

$ 35,300,000

Secured term loan facility, maximum borrowing capacity

$ 54,000,000

Debt instrument, maturity date

Dec. 31, 2027

Long term debt, fixed interest rate

7.50%

United [Member] | Subsequent Event [Member]

Debt Instrument [Line Items]

Repayments of long term debt

10,500,000

United Capacity Purchase Agreement [Member] | Subsequent Event [Member]

Debt Instrument [Line Items]

Repayments of long term debt

$ 10,500,000

United Capacity Purchase Agreement [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Long term debt, basis spread on variable rate

3.50%

3.50%

Revolving loan

$ 10,500,000

Covenant capping restricted payments

5,000,000

Revolving commitments

$ 30,700,000

Rental coverage ratio

1

United Capacity Purchase Agreement [Member] | Revolving Credit Facility [Member] | Subsequent Event [Member]

Debt Instrument [Line Items]

Additional prepayment with potential forgiveness

$ 10,500,000

Additional prepayment with potential forgiveness, outstanding

4,500,000

Forgiveness achieved

750,000

United Capacity Purchase Agreement [Member] | Revolving Credit Facility [Member] | Minimum [Member]

Debt Instrument [Line Items]

Amount required

$ 15,000,000

United Capacity Purchase Agreement [Member] | Revolving Credit Facility [Member] | SOFR [Member]

Debt Instrument [Line Items]

Long term debt, basis spread on variable rate

4.50%

4.50%

United Capacity Purchase Agreement [Member] | United [Member]

Debt Instrument [Line Items]

Percentage of controllable completion factor

99.30%

United Capacity Purchase Agreement [Member] | United [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Amount funded by company

$ 25,500,000

Additional prepayment with potential forgiveness

$ 15,000,000

Forgiveness achieved

9,750,000

United Capacity Purchase Agreement [Member] | United [Member] | Revolving Credit Facility [Member] | Subsequent Event [Member]

Debt Instrument [Line Items]

Additional prepayment with potential forgiveness

15,000,000

Forgiveness achieved

$ 10,500,000

Equipment Notes [Member]

Debt Instrument [Line Items]

Long-Term Debt

$ 108,800,000

Secured Term Loan Facility [Member] | Loan Agreement [Member]

Debt Instrument [Line Items]

Secured term loan facility, maximum borrowing capacity

$ 200,000,000

Debt instrument, maturity date

Oct. 30, 2025

Secured Term Loan Facility [Member] | Loan Agreement [Member] | Treasury Loan [Member]

Debt Instrument [Line Items]

Long term debt, basis spread on variable rate

3.50%

Secured term loan facility, amount borrowed

$ 195,000,000

Secured term loan facility, additional amount borrowed

$ 0

Debt instrument, maturity date

Oct. 30, 2025

Aircraft and Equipment [Member] | Pledged as Collateral [Member]

Debt Instrument [Line Items]

Property and equipment-gross

$ 586,600,000

Loss Per Share - Calculations o

Loss Per Share - Calculations of Net Loss Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share And Equity [Abstract]
Net Income (Loss)	$ (57,850)	$ (9,090)
Basic weighted average common shares outstanding	40,940	36,378
Diluted weighted average common shares outstanding	40,940	36,378
Net loss per share attributable to common shareholders
Basic	$ (1.41)	$ (0.25)
Diluted	$ (1.41)	$ (0.25)

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - $ / shares	Dec. 31, 2023	Sep. 30, 2023
Stockholders' Equity Note [Abstract]
Warrants of common stock exercise price	$ 3.98
Common stock, warrants issued	4,899,497	4,899,497
Common stock, warrants outstanding	4,899,497	4,899,497

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Effective tax rate (ETR) from continuing operations	(1.50%)	9.30%
State net operating loss carryforwards	$ 4.5
Domestic Tax Authority [Member] | 2030-2038 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	560
State and Local Jurisdiction [Member] | 2024-2043 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 247
Minimum [Member] | Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2030
Minimum [Member] | State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year	2024
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	2043

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested share-based compensation arrangements	$ 1,300,000
Unrecognized compensation cost, period for recognition	1 year 6 months
Share-based compensation expense	$ 400,000	$ 700,000
Amounts remitted for employee withholding taxes	$ 0	$ 1,000
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld		847
Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period	1 year
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amounts remitted for employee withholding taxes	$ 0	$ 1,000
Restricted Stock Units [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld	0	847
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

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Restricted Share Activity (Detail) - Restricted Stock [Member]	3 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance | shares	736,891
Number of Shares, Granted | shares	0
Number of Shares, Vested | shares	0
Number of Shares, Forfeited | shares	(8,000)
Number of Shares, Unvested, Ending Balance | shares	728,891
Weighted-Average Grant Date Fair Value, Unvested, Beginning Balance | $ / shares	$ 3.35
Weighted-Average Grant Date Fair Value, Granted | $ / shares	0
Weighted-Average Grant Date Fair Value, Vested | $ / shares	0
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	4.72
Weighted-Average Grant Date Fair Value, Unvested, Ending Balance | $ / shares	$ 3.33

Employee Stock Purchase Plan -

Employee Stock Purchase Plan - Additional Information (Detail) - 2019 ESPP [Member]	3 Months Ended
	Dec. 31, 2023 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares, discount rate	10%
Number of ordinary shares issued	444,590
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%
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%
Number of ordinary shares issued	500,000

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2023 USD ($) AirCraft	Dec. 31, 2022 USD ($) AirCraft
Lessee, Lease, Description [Line Items]
Number of leased aircraft	18
Aggregate rental expense under all operating aircraft, equipment and facility leases | $	$ 7,969	$ 6,907
Weighted average remaining lease term Operating leases	6 years 2 months 12 days
Weighted average discount rate Operating leases	5.80%
RASPRO Aircraft Lease Agreement [Member]
Lessee, Lease, Description [Line Items]
Number of aircraft lease terminated		15
Buyout pricing | $		$ 25,000
RASPRO Aircraft Lease Agreement [Member] | CRJ-900 Aircraft [Member]
Lessee, Lease, Description [Line Items]
Number of leased aircraft	15

Leases - Components of Lease Co

Leases - Components of Lease Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease costs	$ 1,278	$ 4,699
Variable and short-term lease costs	1,279	889
Interest expense on finance lease liabilities	1,289	274
Amortization expense of finance lease assets	4,123	1,046
Total lease costs	$ 7,969	$ 6,907

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - Forward Purchase Contract [Member] - USD ($)	Jul. 31, 2021	Feb. 28, 2021
Heart Aerospace Incorporated [Member] | Maximum [Member]
Purchase Commitment Excluding Longterm Commitment [Line Items]
Purchase commitment amount	$ 1,200,000,000
eVTOL Aircraft [Member] | Archer Aviation, Inc. [Member]
Purchase Commitment Excluding Longterm Commitment [Line Items]
Purchase commitment amount		$ 200,000,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Thousands				3 Months Ended
	Jan. 11, 2024 USD ($) AirCraft	Jan. 01, 2024 USD ($) Engine	Dec. 01, 2023 Engine	Dec. 31, 2023 USD ($) Engine
Subsequent Event [Line Items]
Number of surplus engines to be sold | Engine			12
CF34-8C Aircraft [Member]
Subsequent Event [Line Items]
Number of surplus engines to be sold | Engine				48
Subsequent Event [Member]
Subsequent Event [Line Items]
Gross proceeds from sale of asset		$ 54,200
Proceeds from sale of asset		$ 15,900
Number of aircraft sold	4	12
Subsequent Event [Member] | Minimum [Member]
Subsequent Event [Line Items]
Additional revenue and liquidity	$ 20,400
Subsequent Event [Member] | Maximum [Member]
Subsequent Event [Line Items]
Additional revenue and liquidity	26,800
Subsequent Event [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Repayments of long term debt	2,100
United Capacity Purchase Agreement [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of long term debt	10,500
Realized and unrealized gain on investment		$ 7,200
United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Minimum [Member]
Subsequent Event [Line Items]
Additional revenue and liquidity	20,400
United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Maximum [Member]
Subsequent Event [Line Items]
Additional revenue and liquidity	26,800
United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Additional prepayment with potential forgiveness		10,500
Forgiveness achieved		$ 750
Engine Purchase Agreement [Member] | Subsequent Event [Member] | CF34-8C Aircraft [Member]
Subsequent Event [Line Items]
Number of surplus engines to be sold | Engine		12
Gross proceeds from sale of asset		$ 54,200
Proceeds from sale of asset		15,900
United [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Repayments of long term debt	$ 10,500
United [Member] | United Capacity Purchase Agreement [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Additional prepayment with potential forgiveness				$ 15,000
Forgiveness achieved				$ 9,750
United [Member] | United Capacity Purchase Agreement [Member] | Subsequent Event [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Additional prepayment with potential forgiveness		15,000
Forgiveness achieved		$ 10,500

Subsequent Events - Additiona_2

Subsequent Events - Additional Information (Detail1) $ in Millions

3 Months Ended

Jul. 31, 2024 AirCraft

Jun. 30, 2024 AirCraft

May 31, 2024 AirCraft

May 21, 2024 AirCraft

Apr. 30, 2024 AirCraft

Apr. 22, 2024 AirCraft

Apr. 15, 2024 USD ($)

Mar. 31, 2024 AirCraft

Jan. 01, 2024 USD ($)

Mar. 31, 2024 AirCraft

Dec. 31, 2023 USD ($)

Dec. 31, 2023 AirCraft

Dec. 31, 2023 Airframes

CRJ-900 Aircraft [Member]

Subsequent Event [Line Items]

Number of aircraft to be removed | AirCraft

10

Gross proceeds from sale of asset | $

$ 12

Number of airframes without engines

11

11

Forecast [Member] | CRJ-900 Aircraft [Member]

Subsequent Event [Line Items]

Number of aircraft to be removed | AirCraft

2

2

1

1

2

2

Subsequent Event [Member]

Subsequent Event [Line Items]

Gross proceeds from sale of asset | $

$ 54.2

Proceeds from sale of asset | $

$ 15.9

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Letter Agreement [Member] | Forecast [Member]

Subsequent Event [Line Items]

Buyout price | $

$ 50.3

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement One [Member] | Forecast [Member]

Subsequent Event [Line Items]

Number of engines | AirCraft

30

30

Impact of Pilot Shortage and Transition of Operations to United [Member] | RASPRO Aircraft Lease Agreement Two [Member] | Forecast [Member]

Subsequent Event [Line Items]

Number of airframes without engines | AirCraft

15

15