REVENUE - Cargo and Other Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Total Operating Revenue	$ 4,065	$ 3,704	$ 7,365	$ 6,841
Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	163	139	316	261
Passenger | Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	77	67	136	124
Other Services | Cargo and other revenue
Disaggregation of Revenue [Line Items]
Total Operating Revenue	$ 86	$ 72	$ 180	$ 137