CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 686,955	$ 548,703
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(1,071,637)	(848,897)
Sales of marketable securities	1,041,149	878,070
Acquisition of property and equipment:
Aircraft and rotable spare parts	(223,605)	(170,392)
Buildings and ground equipment	(10,473)	(9,398)
Proceeds from the sale of property and equipment	7,104	1,612
Deposits on aircraft	(100,105)	(625)
Aircraft deposits applied towards acquired aircraft	10,987	9,220
Increase in other assets	(50,205)	(121,037)
NET CASH USED IN INVESTING ACTIVITIES	(396,785)	(261,447)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	213,326	201,285
Principal payments on long-term debt	(448,466)	(117,182)
Net proceeds from issuance of common stock	3,146	2,819
Purchase of treasury stock		(20,000)
Employee income tax paid on vested equity awards	(1,573)	(6,165)
Payment of debt issuance cost	(495)	(3,932)
Payment of cash dividends		(13,059)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(234,062)	43,766
Increase in cash and cash equivalents	56,108	331,022
Cash and cash equivalents at beginning of period	215,723	87,206
CASH AND CASH EQUIVALENTS AT END OF PERIOD	271,831	418,228
Non-cash investing and financing activities:
Acquisition of property and equipment	13,168	8,531
Warrants issued to U.S. Treasury	5,804	8,248
Cash paid during the period for:
Interest, net of capitalized amounts	96,397	95,999
Income taxes	$ 6,374	$ 371