REVENUE - Loyalty Program Liability Rollforward (Details) - Loyalty Plan Revenue - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Change in Contract with Customer, Liability [Roll Forward]
Beginning balance	$ 3,433	$ 3,256
Increase in liability for loyalty points issued	410	414
Ending balance	3,481	3,314
Passenger Services
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	(311)	(307)
Loyalty program other
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	$ (51)	$ (49)