REVENUE - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Receivables - net	$ 586		$ 586		$ 558
Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue recognized	72	$ 46	1,200	$ 763
Loyalty Plan Revenue
Disaggregation of Revenue [Line Items]
Receivables - net	$ 177		$ 177		$ 176