Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating revenues:
Total operating revenues	$ 125,157	$ 73,099	$ 372,808	$ 437,030
Operating expenses:
Flight operations	41,314	29,664	115,681	135,199
Fuel	234	146	822	504
Maintenance	51,986	22,591	156,623	145,021
Aircraft rent	9,648	15,582	29,688	39,196
Aircraft and traffic servicing	682	538	2,326	2,938
General and administrative	12,087	11,737	36,324	39,233
Depreciation and amortization	20,933	20,635	62,108	61,656
Lease termination			4,508
Government grant recognition	(26,101)	(43,018)	(93,379)	(43,018)
Total operating expenses	110,783	57,875	314,701	380,729
Operating income	14,374	15,224	58,107	56,301
Other (expense) income, net:
Interest expense	(8,627)	(10,368)	(26,464)	(34,668)
Interest income	82	1	287	95
Other (expense) income, net	(28)	79	389	720
Total other (expense), net	(8,573)	(10,288)	(25,788)	(33,853)
Income before taxes	5,801	4,936	32,319	22,448
Income tax expense	1,525	1,517	8,236	6,359
Net income and comprehensive income	$ 4,276	$ 3,419	$ 24,083	$ 16,089
Net income per share attributable to common shareholders
Basic	$ 0.12	$ 0.10	$ 0.68	$ 0.46
Diluted	$ 0.11	$ 0.10	$ 0.62	$ 0.46
Weighted-average common shares outstanding
Basic	35,769	35,299	35,642	35,154
Diluted	39,513	35,299	38,811	35,248
Contract Revenue [Member]
Operating revenues:
Total operating revenues	$ 109,654	$ 71,648	$ 318,524	$ 409,228
Pass Through and Other Revenue [Member]
Operating revenues:
Total operating revenues	$ 15,503	$ 1,451	$ 54,284	$ 27,802