Fair value measurements, investments and notes receivable - Narrative (Details) $ in Millions	6 Months Ended
Jun. 30, 2024 USD ($) aircraft
Fair Value [Line Items]
Equity method investments	$ 231
Carrying amount of loan receivable	$ 86
Republic Airways Holdings Inc.
Fair Value [Line Items]
Number of aircraft operated \| aircraft	65
Champlain Enterprises LLC
Fair Value [Line Items]
Number of aircraft operated \| aircraft	53
Republic Airways Holdings Inc.
Fair Value [Line Items]
Ownership stake	19.00%
CommuteAir LLC
Fair Value [Line Items]
Ownership stake	40.00%
United Airlines Ventures Sustainable Flight Fund
Fair Value [Line Items]
Ownership stake	33.00%
Fulcrum BioEnergy, Inc., Boom, Alder Fuels LLC, Heart Aerospace Incorporated and ZeroAvia, Inc.
Fair Value [Line Items]
Investment carrying value	$ 423
Corporate Debt \| Maximum
Fair Value [Line Items]
Available-for-sale securities remaining maturities	2 years

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Fair Value [Line Items]

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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+ References

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Amount of investment in equity security without readily determinable fair value.

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Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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Number of aircraft operated by the carrier.

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