Commitments and Contingencies - Narrative (Details) technician in Thousands, $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	May 01, 2023 USD ($) Contract employee	Jun. 30, 2023 USD ($) employee technician	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) employee technician	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Commitments and Contingencies [Line Items]
Labor contract ratification bonuses		$ 813	$ 0	$ 813	$ 0
International Association Of Machinists National Pension Plan
Commitments and Contingencies [Line Items]
Number of employees | employee	30,000
Number of contracts ratified | Contract	5
Payment for ratification of contracts and taxes	$ 48
Air Line Pilots Association
Commitments and Contingencies [Line Items]
Labor contract ratification bonuses						$ 765
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Number of employees | employee		99,800		99,800
Percentage of employees represented by various U.S. labor organizations				83.00%
Number of technicians | technician		8		8
Bargaining on successor agreement, term				1 year
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		84		84
Floating Rate Debt
Commitments and Contingencies [Line Items]
Long-term debt		11,600		$ 11,600
Remaining term of debt				12 years
Loans and Leases from Non-U.S. Entities
Commitments and Contingencies [Line Items]
Remaining term of debt				12 years
Aggregate balance		$ 8,500		$ 8,500