CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 111,910	$ (8,515)	$ 340,099
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	440,198	474,959	368,098
Stock based compensation expense	8,685	6,802	10,274
Write-off of maintenance assets		3,255
Increase (decrease) in credit loss reserves	(4,249)	17,087
Loss (gain) on disposal of fixed assets	(4,586)	445
Net increase in deferred income taxes	37,305	6,100	109,654
Gain on sale of ExpressJet subsidiary			(46,525)
Special items	84,592		21,869
Changes in operating assets and liabilities:
Decrease (increase) in receivables	(30,093)	26,831	(40,700)
Decrease (increase) in income tax receivable	(5,570)	7,225	14,795
Decrease (increase) in inventories	(12,897)	19,307	(4,303)
Decrease (increase) in other current assets	(1,936)	8,233	2,707
Decrease in operating lease right-of-use assets	43,846	53,647
Decrease in operating lease liabilities	(51,326)	(65,557)	(895)
Increase (decrease) in deferred revenue	(6,832)	110,728
Increase in unbilled revenue	(8,404)
Increase (decrease) in accounts payable and other current liabilities	231,177	(26,984)	(54,043)
NET CASH PROVIDED BY OPERATING ACTIVITIES	831,820	633,563	721,030
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(1,517,861)	(1,347,775)	(1,938,750)
Sales of marketable securities	1,526,057	1,170,556	1,866,761
Net cash received from sale of ExpressJet subsidiary			53,200
Acquisition of property and equipment:
Aircraft and rotable spare parts	(537,574)	(425,618)	(581,329)
Buildings and ground equipment	(18,127)	(12,678)	(80,586)
Proceeds from the sale of property and equipment	7,117	3,239	26,008
Deposits on aircraft	(125,701)	(9,625)	(52,817)
Aircraft deposits applied towards acquired aircraft	32,962	27,858	46,346
Decrease (increase) in other assets	(65,395)	(89,428)	4,133
NET CASH USED IN INVESTING ACTIVITIES	(698,522)	(683,471)	(657,034)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	450,032	406,364	200,040
Principal payments on long-term debt	(540,537)	(187,404)	(382,442)
Net proceeds from issuance of common stock	3,146	2,819	6,271
Purchase of treasury stock		(20,000)	(78,476)
Purchase of common stock			(16,145)
Employee income tax paid on vested equity awards	(1,576)	(6,165)	(9,313)
Payment of debt issuance cost	(1,665)	(4,130)	(1,642)
Payment of cash dividends		(13,059)	(23,467)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(90,600)	178,425	(305,174)
Increase (decrease) in cash and cash equivalents	42,698	128,517	(241,178)
Cash and cash equivalents at beginning of period	215,723	87,206	328,384
CASH AND CASH EQUIVALENTS AT END OF PERIOD	258,421	215,723	87,206
Non-cash investing and financing activities:
Acquisition of property and equipment	11,336	22,187	16,514
Debt assumed on aircraft acquired under operating leases			14,475
Engines contributed to joint venture			22,313
Non-cash assets used to acquire aircraft under operating leases			153,566
Lease liability arising from the recognition of right-of-use asset			456,472
Warrants issued to U.S. Treasury	5,804	8,248
Cash paid during the period for:
Interest, net of capitalized amounts	124,918	125,440	131,733
Income taxes	$ 6,589	$ 1,780	2,490
SUPPLEMENTAL DISCLOSURE OF SALE OF SUBSIDIARY:
Decrease in carrying amount of assets			(101,448)
Decrease in carrying amount of liabilities			68,341
Cash received from buyers			79,632
Gain on sale of subsidiary			$ 46,525