CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 582,468	$ 573,127
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(1,469,091)	(1,575,991)
Sales of marketable securities	1,566,471	1,699,284
Proceeds from the sale of aircraft, property and equipment	25,604
Acquisition of property and equipment:
Aircraft and rotable spare parts	(419,508)	(848,723)
Buildings and ground equipment	(61,021)	(35,870)
Deposits on aircraft	(31,817)
Aircraft deposits applied towards acquired aircraft	23,298	21,421
Net cash received from sale of ExpressJet subsidiary	53,200
Decrease (increase) in other assets	7,570	(2,479)
NET CASH USED IN INVESTING ACTIVITIES	(305,294)	(742,358)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	99,914	626,163
Principal payments on long-term debt	(291,250)	(262,923)
Net proceeds from issuance of common stock	6,270	5,212
Purchase of treasury and common stock and employee income tax paid on equity awards	(93,935)	(38,720)
Increase in debt issuance cost	(1,242)	(3,182)
Payment of cash dividends	(17,406)	(14,550)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(297,649)	312,000
Increase (decrease) in cash and cash equivalents	(20,475)	142,769
Cash and cash equivalents at beginning of period	328,384	181,792
CASH AND CASH EQUIVALENTS AT END OF PERIOD	307,909	324,561
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Acquisition of rotable spare parts	3,662	10,346
Debt assumed on aircraft acquired under operating leases	14,475	59,132
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
Cash paid during the period for:
Interest, net of capitalized amounts	100,100	85,611
Income taxes	2,415	$ 2,382
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