REVENUE - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Disaggregation of Revenue [Line Items]
Receivables - net	$ 681		$ 681		$ 565
Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue recognized	207	$ 211	991	$ 1,100
Loyalty Plan Revenue
Disaggregation of Revenue [Line Items]
Receivables - net	$ 168		$ 168		$ 154