REVENUE - Loyalty Program Liability Rollforward (Details) - Loyalty Plan Revenue - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Change in Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 3,433	$ 3,256
Increase in liability for loyalty points issued	859	990
Ending balance	3,530	3,472
Passenger Services
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	(656)	(655)
Loyalty program other
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	$ (106)	$ (119)