Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2022 USD ($) employee aircraft	Jun. 30, 2022 USD ($) employee aircraft	Jul. 21, 2022 aircraft
Commitments and Contingencies [Line Items]
Loss contingency, loss in period	$ 94	$ 94
Remaining term of debt		10 years
Boeing 737 MAX
Commitments and Contingencies [Line Items]
Sale leaseback transaction, number of leased assets expected to be purchased in next fiscal year | aircraft	8	8
Boeing 737 MAX | Subsequent Event
Commitments and Contingencies [Line Items]
Number of aircraft expected to take delivery that are delayed | aircraft			7
Boeing 787 | Subsequent Event
Commitments and Contingencies [Line Items]
Number of aircraft expected to take delivery that are delayed | aircraft			3
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Number of employees | employee	91,200	91,200
Percentage of employees represented by various U.S. labor organizations		85.00%
Tax-Exempt Special Facilities Revenue Bonds
Commitments and Contingencies [Line Items]
Aggregate principal amount of guarantee	$ 2,000	$ 2,000
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Aggregate principal amount of guarantee	99	99
Floating Rate Debt
Commitments and Contingencies [Line Items]
Debt	13,100	$ 13,100
Loans and Leases from Non-U.S. Entities
Commitments and Contingencies [Line Items]
Remaining term of debt		10 years
Aggregate balance	$ 9,900	$ 9,900