CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 99	$ 184
Related to marketable securities:
Unrealized holding gains arising during the period	3	12
Income tax effect	(1)	(4)
Total	2	8
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits	6	5
Income tax effect	(2)	(2)
Total	4	3
Related to interest rate derivative instruments:
Unrealized holding gains (losses) arising during the period	1	(5)
Reclassification of losses into Aircraft rent	0	1
Income tax effect	(1)	2
Total	0	(2)
Other Comprehensive Income	6	9
Comprehensive Income	$ 105	$ 193