Consolidated Statements of Operations and Comprehensive (Loss) Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Operating revenues:
Contract revenue	$ 498,065	$ 531,001	$ 503,591
Operating expenses:
Flight operations	216,748	177,038	162,137
Maintenance	199,648	201,930	217,646
Aircraft rent	6,200	36,989	39,345
General and administrative	48,765	43,966	49,855
Depreciation and amortization	60,359	81,508	82,847
Lease termination		233	4,508
Asset impairment	54,343	171,824
(Gain) on sale of assets	(7,162)	(4,723)	78
Other operating expenses	3,510	7,238	3,536
Government grant recognition			(119,479)
Total operating expenses	582,411	716,003	440,395
Operating (loss)/income	(84,346)	(185,002)	63,196
Other income (expense), net:
Interest expense	(49,921)	(35,289)	(34,730)
Interest income	146	139	365
Unrealized gain/(loss) on investments, net	5,408	(13,715)	(6,816)
Other (expense)/income, net	(148)	(801)	401
Total other expense, net	(44,515)	(49,666)	(40,780)
(Loss)/income before taxes	(128,861)	(234,668)	22,416
Income tax (benefit)/expense	(8,745)	(51,990)	5,828
Net (loss)/income and comprehensive (loss)/income	$ (120,116)	$ (182,678)	$ 16,588
Net loss per share attributable to common shareholders
Basic	$ (3.04)	$ (5.06)	$ 0.46
Diluted	$ (3.04)	$ (5.06)	$ 0.43
Weighted-average common shares outstanding
Basic	39,465	36,133	35,713
Diluted	39,465	36,133	38,843
Contract Revenue
Operating revenues:
Contract revenue	$ 421,298	$ 478,482	$ 434,518
Pass Through and Other Revenue
Operating revenues:
Contract revenue	$ 76,767	$ 52,519	$ 69,073