REVENUE - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Disaggregation of Revenue [Line Items]
Receivables - net	$ 656		$ 656		$ 565
Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue recognized	85	$ 72	1,100	$ 1,200
Loyalty Plan Revenue
Disaggregation of Revenue [Line Items]
Receivables - net	$ 171		$ 171		$ 154