REVENUE - Loyalty Program Liability Rollforward (Details) - Loyalty Plan Revenue - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025
Change in Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 3,433	$ 3,256
Increase in liability for loyalty points issued	1,284	1,364
Ending balance	3,544	3,433
Passenger Services
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	(1,001)	(993)
Loyalty program other
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	$ (172)	$ (194)