CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 34,342	$ 72,953	$ 111,910
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	383,115	394,552	440,198
Stock based compensation expense	17,125	9,159	8,685
Decrease in credit loss reserves	(185)	(4,591)	(4,249)
Gain on disposal of fixed assets	(14,295)	(7,948)	(4,586)
Loss (gain) on investments in other companies	479	(11,380)
Net increase in deferred income taxes	539	23,825	37,305
Impairment on assets held for sale	2,318	51,384
Special items			84,592
Changes in operating assets and liabilities:
Decrease (increase) in receivables	19,818	(32,959)	(30,093)
Decrease (increase) in income tax receivable	997	7,815	(5,570)
Increase in inventories	(3,905)	(16,628)	(12,897)
Decrease (increase) in other current assets	1,593	(2,871)	(1,936)
Decrease in operating lease right-of-use assets	25,954	86,588	43,846
Decrease in operating lease liabilities	(54,984)	(76,812)	(51,326)
Increase (decrease) in deferred revenue	229,862	40,812	(6,832)
Decrease (increase) in unbilled revenue	12,601	(11,491)	(8,404)
Increase (decrease) in accounts payable and other current liabilities	80,960	(42,032)	231,177
NET CASH PROVIDED BY OPERATING ACTIVITIES	736,334	480,376	831,820
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(1,339,465)	(1,834,403)	(1,517,861)
Sales of marketable securities	1,600,877	1,488,359	1,526,057
Acquisition of property and equipment:
Aircraft and rotable spare parts	(238,068)	(632,460)	(537,574)
Buildings and ground equipment	(13,258)	(13,031)	(18,127)
Proceeds from the sale of property and equipment	15,879	16,983	7,117
Deposits on aircraft	(65,000)	(37,100)	(125,701)
Aircraft deposits applied towards acquired aircraft	11,649	138,383	32,962
Decrease (increase) in other assets	4,158	(31,625)	(65,395)
NET CASH USED IN INVESTING ACTIVITIES	(23,228)	(904,894)	(698,522)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	69,689	684,502	450,032
Principal payments on long-term debt	(447,604)	(415,050)	(540,537)
Payment of debt issuance cost	(175)	(2,178)	(1,665)
Net proceeds from issuance of common stock	2,811	2,957	3,146
Employee income tax paid on vested equity awards	(585)	(1,150)	(1,576)
Purchase of treasury stock and related excise tax	(291,949)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(667,813)	269,081	(90,600)
Increase (decrease) in cash and cash equivalents	45,293	(155,437)	42,698
Cash and cash equivalents at beginning of period	102,984	258,421	215,723
CASH AND CASH EQUIVALENTS AT END OF PERIOD	148,277	102,984	258,421
Non-cash investing and financing activities:
Acquisition of property and equipment	12,583	16,826	11,336
Derecognition of right of use assets	(39,247)
Derecognition of operating lease liabilities	39,247
Warrants issued to U.S. Treasury			5,804
Cash paid during the period for:
Interest, net of capitalized amounts	128,288	125,321	124,918
Income taxes	$ 13,610	$ 1,166	$ 6,589