REVENUE - Cargo and Other Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disaggregation of Revenue [Line Items]
Total Operating Revenue	$ 4,308	$ 3,766	$ 11,673	$ 10,607
Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	160	142	476	403
Passenger | Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	74	70	210	194
Other Services | Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	$ 86	$ 72	$ 266	$ 209