CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CONSOLIDATED STATEMENTS OF CASH FLOWS
NET CASH PROVIDED BY OPERATING ACTIVITIES	$ 362,123	$ 350,822
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(896,326)	(1,377,448)
Sales of marketable securities	961,403	1,407,623
Proceeds from the sale of aircraft, property and equipment	21,065
Acquisition of property and equipment:
Aircraft and rotable spare parts	(325,969)	(553,877)
Buildings and ground equipment	(55,865)	(19,070)
Deposits on aircraft	(31,817)
Aircraft deposits applied towards acquired aircraft	23,298
Net cash received from sale of ExpressJet subsidiary	53,200
Decrease (increase) in other assets	1,962	(4,962)
NET CASH USED IN INVESTING ACTIVITIES	(249,049)	(547,734)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	99,914	383,644
Principal payments on long-term debt	(211,200)	(160,387)
Net proceeds from issuance of common stock	4,540	2,320
Purchase of treasury and common stock and employee income tax paid on equity awards	(68,932)	(23,467)
Increase in debt issuance cost	(820)	(1,917)
Payment of cash dividends	(11,299)	(9,345)
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	(187,797)	190,848
Increase (decrease) in cash and cash equivalents	(74,723)	(6,064)
Cash and cash equivalents at beginning of period	328,384	181,792
CASH AND CASH EQUIVALENTS AT END OF PERIOD	253,661	175,728
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Acquisition of rotable spare parts	3,244	426
Debt assumed on aircraft acquired under operating leases	14,475	59,132
Engines contributed to joint venture	22,313
Right of use assets applied to aircraft acquired under operating leases	150,688
Lease liability arising from the recognition of right-of-use asset	456,472
Cash paid during the period for:
Interest, net of capitalized amounts	67,778	54,765
Income taxes	1,713	$ 1,852
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