REVENUE - Cargo and Other Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Total Operating Revenue	$ 3,300	$ 3,137
Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	153	122
Passenger | Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	59	57
Other Services | Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	$ 94	$ 65