REVENUE - Passenger Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue	$ 14,239	$ 11,735	$ 10,426
Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue	12,835	10,654	9,526
Passenger revenue | Domestic
Disaggregation of Revenue [Line Items]
Revenue	11,631	9,831	8,938
Passenger revenue | Latin America
Disaggregation of Revenue [Line Items]
Revenue	674	677	588
Passenger revenue | Pacific
Disaggregation of Revenue [Line Items]
Revenue	530	146	0
Passenger ticket revenue, net of taxes and fees | Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue	10,762	8,926	8,016
Passenger ancillary revenue | Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue	646	548	476
Loyalty program passenger revenue | Passenger revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 1,427	$ 1,180	$ 1,034