Condensed Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net income (loss)	$ 56,076	$ (44,922)
Adjustments to reconcile net income to net cash provided by operations:
Losses reclassified from other comprehensive income	74	79
Share-based compensation	3,671	3,075
Amortization of deferred gains and losses and debt issuance costs	2,289	1,624
Depreciation and amortization	50,726	39,373
Deferred income tax expense (benefit)	11,647	(20,266)
Loss on disposal of assets	1,913	848
Special charges, non-operating	0	9,201
Changes in operating assets and liabilities:
Accounts receivable	(23,285)	(2,983)
Aircraft maintenance deposits, net	(2,559)	14,844
Long-term deposits and other assets	20,735	3,512
Deferred heavy maintenance, net	(44,161)	(50,712)
Accounts payable	(13,543)	6,227
Air traffic liability	111,020	93,483
Other liabilities	30,712	117,779
Other	(164)	(27)
Net cash provided by operating activities	205,151	171,135
Investing activities:
Purchase of available-for-sale investment securities	(26,476)	(30,853)
Proceeds from the maturity of available-for-sale investment securities	26,085	30,504
Pre-delivery deposits on flight equipment, net of refunds	(37,913)	(41,580)
Capitalized interest	(2,276)	(1,500)
Assets under construction for others	(262)	0
Purchase of property and equipment	(63,109)	(237,221)
Net cash used in investing activities	(103,951)	(280,650)
Financing activities:
Proceeds from issuance of long-term debt	59,706	227,128
Proceeds from stock options exercised	0	2
Payments on debt obligations	(37,901)	(18,650)
Payments on finance lease obligations	(239)	(197)
Reimbursement for assets under construction for others	262	0
Repurchase of common stock	(5,223)	(959)
Debt issuance costs	(399)	(201)
Net cash provided by financing activities	16,206	207,123
Net increase in cash and cash equivalents	117,406	97,608
Cash and cash equivalents at beginning of period	1,004,733	800,849
Cash and cash equivalents at end of period	1,122,139	898,457
Cash payments for:
Interest, net of capitalized interest	19,167	8,569
Income taxes paid, net of refunds	816	679
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	47,577	0
Operating cash flows for finance leases	210	0
Financing cash flows for finance leases	29	0
Non-cash transactions:
Capital expenditures funded by finance lease borrowings	1,492	237,042
Capital expenditures funded by operating lease borrowings	$ 128,191	$ 0