CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net Income	$ 274	$ 198	$ 657	$ 457
Related to marketable securities:
Unrealized holding gains (losses) arising during the period	0	(4)	2	3
Reclassification of (gains) losses into Other-net nonoperating income (expense)	0	(1)	0	(2)
Income tax effect	0	2	(1)	0
Total	0	(3)	1	1
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits	3	2	11	7
Income tax effect	(1)	(1)	(4)	(3)
Total	2	1	7	4
Related to interest rate derivative instruments:
Unrealized holding gains (losses) arising during the period	(5)	0	(8)	(5)
Reclassification of (gains) losses into Aircraft rent	2	2	5	5
Income tax effect	2	0	2	0
Total	(1)	2	(1)	0
Other Comprehensive Income	1	0	7	5
Comprehensive Income	$ 275	$ 198	$ 664	$ 462