CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
OPERATING REVENUES:
Total operating revenues	$ 760,295	$ 829,275	$ 2,228,372	$ 2,418,190
OPERATING EXPENSES:
Salaries, wages and benefits	251,414	301,378	752,768	901,775
Depreciation and amortization	92,795	86,088	272,929	246,386
Special items			21,869
Other operating expenses	59,577	68,859	184,634	206,511
Total operating expenses	613,854	691,350	1,841,419	2,065,412
OPERATING INCOME	146,441	137,925	386,953	352,778
OTHER INCOME (EXPENSE):
Interest income	3,542	2,283	11,081	5,692
Interest expense	(31,606)	(31,440)	(96,884)	(86,485)
Other income (expense), net	361	1,157	47,367	3,470
Total other expense, net	(27,703)	(28,000)	(38,436)	(77,323)
INCOME BEFORE INCOME TAXES	118,738	109,925	348,517	275,455
PROVISION FOR INCOME TAXES	27,399	26,879	80,945	62,189
NET INCOME	$ 91,339	$ 83,046	$ 267,572	$ 213,266
BASIC EARNINGS PER SHARE (in dollars per share)	$ 1.80	$ 1.60	$ 5.24	$ 4.10
DILUTED EARNINGS PER SHARE (in dollars per share)	$ 1.79	$ 1.57	$ 5.19	$ 4.03
Weighted average common shares:
Basic (in shares)	50,746	52,039	51,111	52,002
Diluted (in shares)	51,129	52,981	51,568	52,976
COMPREHENSIVE INCOME:
Net income	$ 91,339	$ 83,046	$ 267,572	$ 213,266
Net unrealized appreciation on debt securities, net of taxes		(2)	32	32
TOTAL COMPREHENSIVE INCOME	91,339	83,044	267,604	213,298
Flying agreements
OPERATING REVENUES:
Total operating revenues	738,838	816,057	2,164,173	2,377,659
Airport customer service and other
OPERATING REVENUES:
Total operating revenues	21,457	13,218	64,199	40,531
Aircraft maintenance, materials and repairs
OPERATING REVENUES:
Total operating revenues	133,521	142,285	376,572	423,665
Aircraft fuel
OPERATING REVENUES:
Total operating revenues	31,063	30,258	87,570	87,208
Airport related expenses
OPERATING REVENUES:
Total operating revenues	27,808	25,655	89,237	80,852
Aircraft rentals
OPERATING REVENUES:
Total operating revenues	$ 17,676	$ 36,827	$ 55,840	$ 119,015