Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 47,580,000	$ 33,255,000	$ 32,828,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	77,994,000	65,031,000	61,048,000
Stock compensation expense	5,508,000	12,929,000	1,288,000
Deferred income taxes	15,503,000	(17,874,000)	20,515,000
Amortization of unfavorable lease liabilities and deferred credits	(10,839,000)	(11,035,000)	(10,626,000)
Amortization of debt financing costs and accretion of interest on non-interest-bearing subordinated notes	4,203,000	4,606,000	2,689,000
Loss on extinguishment of debt	3,616,000
(Gain)/loss on disposal of assets	(5,000)	307,000	533,000
Provision for obsolete expendable parts and supplies	642,000	200,000	419,000
Lease termination	9,540,000	15,109,000
Provision for doubtful accounts			(86,000)
Changes in assets and liabilities:
Receivables	(9,275,000)	(5,437,000)	530,000
Expendable parts and supplies	(6,310,000)	(744,000)	(3,379,000)
Prepaid expenses and other current assets	(713,000)	7,584,000	(17,243,000)
Accounts payable	12,119,000	2,427,000	(17,336,000)
Accrued liabilities	2,113,000	12,581,000	3,547,000
Net cash provided by operating activities	151,676,000	118,939,000	74,727,000
Cash flows used in investing activities:
Capital expenditures	(125,350,000)	(117,989,000)	(84,500,000)
Purchases of investment securities	(14,884,000)	(19,921,000)
Sales of investment securities	34,961,000
Proceeds from sale of rotable spare parts			18,000
Net returns (payments) of lease and equipment deposits	431,000	(653,000)	406,000
Net cash used in investing activities	(104,842,000)	(138,563,000)	(84,076,000)
Cash flows from financing activities:
Proceeds from long-term debt	171,658,000	187,703,000	185,912,000
Principal payments on long-term debt and capital leases	(244,087,000)	(222,153,000)	(152,995,000)
Debt financing costs	(5,680,000)	(5,852,000)	(3,377,000)
Debt prepayment costs	(1,672,000)
Proceeds from issuance of common stock		124,246,000
Stock issuance costs	185,000	(12,540,000)
Repurchase of stock	(1,871,000)	(4,993,000)	(1,043,000)
Net cash (used in) provided by financing activities	(81,467,000)	66,411,000	28,497,000
Net change in cash and cash equivalents	(34,633,000)	46,787,000	19,148,000
Cash and cash equivalents and restricted cash at beginning of period	107,134,000	60,347,000	41,199,000
Cash and cash equivalents and restricted cash at end of period	72,501,000	107,134,000	60,347,000
Supplemental cash flow information
Cash paid for interest	53,503,000	50,672,000	43,798,000
Cash paid for income taxes - net	419,000	385,000	332,000
Supplemental non-cash investing and financing activities
Accrued capital expenditures	$ 179,000	16,677,000	$ 9,533,000
Acquisition of capital leases		$ 10,473,000