CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Income (Loss)	$ (1,324)	$ 769	$ 437
Related to marketable securities:
Unrealized holding gains (losses) arising during the period	33	31	(14)
Reclassification of (gains) losses into Other-net non-operating income (expense)	(14)	(5)	8
Income tax benefit (expense)	(5)	(6)	2
Marketable securities, net of tax	14	20	(4)
Related to employee benefit plans:
Actuarial losses related to pension and other postretirement benefit plans	(69)	(71)	(34)
Reclassification of net pension expense into Wages and benefits and Other-net non-operating income	30	32	28
Income tax benefit (expense)	10	10	2
Employee benefit plans, net of tax	29	29	4
Related to interest rate derivative instruments:
Unrealized holding gains (losses) arising during the period	(21)	(13)	0
Reclassification of losses into Aircraft rent	3	3	3
Income tax benefit (expense)	4	2	(1)
Interest rate derivative instruments, net of tax	(14)	(8)	2
Other comprehensive income (loss)	(29)	(17)	(6)
Comprehensive income	$ (1,353)	$ 752	$ 431