Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net (Loss)/Income	$ (120,116)	$ (182,678)	$ 16,588
Adjustments to reconcile net loss to net cash flows provided by (used in)) operating activities:
Depreciation and amortization	60,359	81,508	82,847
Stock compensation expense	2,275	2,761	3,126
Unrealized (gain)/loss on investments, net	(5,408)	13,715	6,816
Deferred income taxes	(9,304)	(52,221)	5,665
Amortization of deferred credits	1,535	(852)	(2,357)
Amortization of debt discount and issuance costs and accretion of interest into long-term debt	6,324	9,681	11,379
Asset impairment	54,343	171,824
(Gain) on sale of assets	(7,162)	(4,723)	78
Loss/(Gain) on extinguishment of debt	1,505	397	(950)
Other	2,236	867	4,888
Changes in assets and liabilities:
Receivables	(4,275)	(811)	10,545
Expendable parts and supplies	(2,530)	(2,882)	(1,865)
Prepaid expenses and other operating assets and liabilities	(769)	(679)	(56)
Accounts payable	496	(2,772)	7,861
Deferred heavy maintenance, net	(1,382)	(8,066)	(3,857)
Deferred revenue	(3,020)	(10,432)	10,742
Accrued expenses and other liabilities	(3,938)	(3,175)	(8,911)
Operating lease right-of-use assets and liabilities	4,740	1,900	(9,668)
Net cash (used in) provided by operating activities	(24,091)	13,362	132,871
Cash flows from investing activities:
Capital expenditures	(36,641)	(40,814)	(17,149)
Investments in equity securities		(200)	(10,000)
Proceeds from sale of aircraft and engines	178,644	50,000
Refund (payment) of equipment and other deposits	282	(7,621)	(6,322)
Net cash provided by (used in) investing activities	142,285	1,365	(33,471)
Cash flows from financing activities:
Proceeds from long-term debt	60,878	39,811	195,000
Principal payments on long-term debt and finance leases	(203,029)	(114,910)	(271,033)
Payments of debt and warrant issuance costs	(917)	(2,414)	(1,326)
Proceeds from issuance of common stock under ESPP	284	399	471
Payment of tax withholding for RSUs	(363)	(455)	(1,486)
Net cash used in financing activities	(143,147)	(77,569)	(78,374)
Net change in cash, cash equivalents and restricted cash	(24,953)	(62,842)	21,026
Cash, cash equivalents and restricted cash at beginning of period	61,025	123,867	102,841
Cash, cash equivalents and restricted cash at end of period	36,072	61,025	123,867
Supplemental cash flow information
Cash paid for interest	38,410	24,895	32,767
Cash paid for income taxes, net	419	487	404
Operating lease payments in operating cash flows	9,476	36,262	47,612
Supplemental non-cash operating activities
Right-of-use assets obtained in exchange for lease liabilities	2,919	6,286	4,309
Supplemental non-cash financing activities
Finance lease obtained in exchange for lease liability	65,481
Acquisition of finance leases		15,122	15,122
Investments in warrants to purchase common stock		3,260	21,964
Accrued capital expenditures	$ 196	$ 1,121	439
Debt issuance cost related to loan agreement with U.S. Department of the Treasury			$ (1,887)