Condensed Statements of Cash Flows (unaudited) - USD ($)		3 Months Ended				6 Months Ended		9 Months Ended
		Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Operating activities:
Net income (loss)		$ (144,428,000)	$ (27,828,000)	$ 114,501,000	$ 56,076,000	$ (172,256,000)	$ 170,577,000
Adjustments to reconcile net income (loss) to net cash provided by operations:
Losses reclassified from other comprehensive income						128,000	148,000
Share-based compensation						6,442,000	6,413,000
Allowance for doubtful accounts (recoveries)						(226,000)	0
Amortization of deferred gains, losses and debt issuance costs						4,633,000	4,365,000
Depreciation and amortization		69,113,000		54,913,000		135,104,000	105,639,000	$ 105,639,000
Accretion of convertible debt						2,029,000	0
Deferred income tax expense						31,518,000	44,511,000
Loss on disposal of assets		0		1,550,000		0	3,463,000
Changes in operating assets and liabilities:
Accounts receivable, net						17,360,000	(30,465,000)
Aircraft maintenance deposits, net						11,254,000	(6,214,000)
Prepaid income taxes						0	1,962,000
Long-term deposits and other assets						(16,717,000)	10,212,000
Deferred heavy maintenance						(57,306,000)	(88,350,000)
Income tax receivable						(125,948,000)	0
Accounts payable						(6,477,000)	2,024,000
Air traffic liability						136,615,000	111,009,000
Deferred salaries, wages and benefits, net						114,052,000	0
Other liabilities						(127,204,000)	6,154,000
Other						40,000	(424,000)
Net cash provided (used) by operating activities						(46,959,000)	341,024,000
Investing activities:
Purchase of available-for-sale investment securities						(54,992,000)	(57,355,000)
Proceeds from the maturity and sale of available-for-sale investment securities						54,195,000	56,595,000
Pre-delivery deposits on flight equipment, net of refunds						(153,353,000)	(75,826,000)
Capitalized interest						(6,289,000)	(4,936,000)
Assets under construction for others						(2,282,000)	(2,235,000)
Purchase of property and equipment						(294,633,000)	(154,702,000)
Net cash used in investing activities						(457,354,000)	(238,459,000)
Financing activities:
Proceeds from issuance of long-term debt						674,146,000	94,706,000
Proceeds from issuance of common stock and warrants						203,723,000	0
Proceeds from stock options exercised						39,000	1,000
Payments on debt obligations						(149,429,000)	(85,785,000)
Payments on finance lease obligations						(25,020,000)	(1,796,000)
Reimbursement for assets under construction for others						2,322,000	2,235,000
Repurchase of common stock						(1,554,000)	(5,248,000)
Long-term debt and equity issuance costs						(21,411,000)	(614,000)
Net cash provided by financing activities						682,816,000	3,499,000
Net increase (decrease) in cash, cash equivalents, and restricted cash						178,503,000	106,064,000
Cash and cash equivalents at beginning of period			$ 978,957,000		$ 1,004,733,000	978,957,000	1,004,733,000	$ 1,004,733,000
Cash, cash equivalents, and restricted cash at end of period (1)	[1]	$ 1,157,460,000		$ 1,110,797,000		1,157,460,000	1,110,797,000
Cash payments for:
Interest, net of capitalized interest						37,636,000	41,279,000
Income taxes paid (received), net						(19,631,000)	7,394,000
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases						103,127,000	95,643,000
Financing cash flows for finance leases						139,000	339,000
Non-cash transactions:
Capital expenditures funded by finance lease borrowings						565,000	96,371,000
Capital expenditures funded by operating lease borrowings						$ 120,961,000	$ 159,548,000

[1] (1) The sum of cash and cash equivalents and restricted cash on our condensed balance sheets equals cash, cash equivalents, and restricted cash in our statement of cash flows.