Revenue - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Movement in Deferred Revenue
Air traffic liability - loyalty program - beginning balance	$ 3,561	$ 3,171	$ 3,385	$ 3,011
Amounts deferred associated with points awarded	385	757	1,041	1,468
Revenue recognized from points redeemed - Passenger	(81)	(622)	(542)	(1,158)
Revenue recognized from points redeemed - Other	(9)	(17)	(28)	(32)
Air traffic liability - loyalty program - ending balance	$ 3,856	$ 3,289	$ 3,856	$ 3,289