CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 231,593	$ 269,483
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(332,865)	(236,527)
Sales of marketable securities	337,612	381,142
Acquisition of property and equipment:
Aircraft and rotable spare parts	(51,904)	(73,482)
Buildings and ground equipment	(4,224)	(3,542)
Proceeds from the sale of property and equipment	2,150	1,366
Deposits on aircraft	(5,000)
Increase in other assets	(67,176)	(13,970)
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(121,407)	54,987
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	39,931
Principal payments on long-term debt	(135,007)	(89,796)
Net proceeds from issuance of common stock	1,745	1,532
Purchase of treasury stock		(20,000)
Employee income tax paid on vested equity awards	(1,573)	(6,165)
Payment of debt issuance cost		(1,664)
Payment of cash dividends		(6,039)
NET CASH USED IN FINANCING ACTIVITIES	(94,904)	(122,132)
Increase in cash and cash equivalents	15,282	202,338
Cash and cash equivalents at beginning of period	215,723	87,206
CASH AND CASH EQUIVALENTS AT END OF PERIOD	231,005	289,544
Non-cash investing and financing activities:
Acquisition of rotable spare parts	1,380	34,100
Warrants issued to U.S. Treasury	3,291
Cash paid during the period for:
Interest, net of capitalized amounts	31,646	31,413
Income taxes	$ 157	$ 126