CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ (431)	$ 322	$ (877)	$ 588
Related to marketable securities:
Unrealized holding gain (loss) arising during the period	2	4	32	31
Reclassification of (gain) loss into Other - net nonoperating income (expense)	(2)	(5)	(11)	(3)
Income tax effect	0	0	(5)	(7)
Total	0	(1)	16	21
Related to employee benefit plans:
Reclassification of net pension expense into Wages and benefits and Other - net nonoperating income (expense)	7	8	22	24
Income tax effect	(1)	(2)	(5)	(6)
Total	6	6	17	18
Related to interest rate derivative instruments:
Unrealized holding gain (loss) arising during the period	2	(5)	(25)	(17)
Reclassification of loss into Aircraft rent	1	1	2	2
Income tax effect	(1)	0	5	3
Total	2	(4)	(18)	(12)
Other Comprehensive Income (Loss)	8	1	15	27
Comprehensive Income (Loss)	$ (423)	$ 323	$ (862)	$ 615