Investments - Schedule of Equity Investments (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	$ 144	$ 146
American Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	144	146
Equity Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	532	603
Equity Securities | American Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 532	$ 603
China Southern Airlines
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Ownership interest, fair value method investments	1.50%	1.50%
Carrying value, fair value method investments	$ 135	$ 203
China Southern Airlines | American Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Ownership interest, fair value method investments	1.50%	1.50%
Carrying value, fair value method investments	$ 135	$ 203
Republic Airways Holdings Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Ownership interest, equity method investments	20.80%	20.80%
Carrying value, equity method investments	$ 253	$ 254
Republic Airways Holdings Inc. | American Airlines, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Ownership interest, equity method investments	20.80%	20.80%
Carrying value, equity method investments	$ 253	$ 254