REVENUE - Air Traffic Liability - Loyalty Program Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Air Traffic Liability [Roll Forward]
Air traffic liability - loyalty program - beginning balance	$ 4,916	$ 5,189
Amounts deferred associated with points awarded	3,532	3,466
Air traffic liability - loyalty program - ending balance	4,849	4,916
Passenger
Air Traffic Liability [Roll Forward]
Revenue recognized from points redeemed	(3,484)	(3,639)
Other
Air Traffic Liability [Roll Forward]
Revenue recognized from points redeemed	$ (115)	$ (100)