REVENUE - Loyalty Program Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 14,239	$ 11,735	$ 10,426
Loyalty Plan Revenue
Disaggregation of Revenue [Line Items]
Revenue	2,282	1,913	1,682
Passenger | Loyalty Plan Revenue
Disaggregation of Revenue [Line Items]
Revenue	1,427	1,180	1,034
Loyalty program other | Loyalty Plan Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 855	$ 733	$ 648