Commitments and Contingencies - Narrative (Details) technician in Thousands		1 Months Ended	4 Months Ended	12 Months Ended
	May 01, 2023 USD ($)	Sep. 30, 2023	Dec. 31, 2023 USD ($) employee	Dec. 31, 2023 USD ($) employee option	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	May 31, 2023 contract employee	Jan. 31, 2023 technician
Commitments and Contingencies [Line Items]
Gross capital expenditures				$ 7,171,000,000	$ 4,819,000,000	$ 2,107,000,000
Loss contingency, loss in period					94,000,000
Aggregate balance			$ 3,243,000,000	$ 3,243,000,000
Number of call options to purchase regional jet aircraft | option				252
IAM 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	$ 48,000,000
Air Line Pilots Association
Commitments and Contingencies [Line Items]
Agreement in principle pay rate increase period		4 years
Expenses associated with AIP			$ 765,000,000
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Gross capital expenditures				$ 7,171,000,000	$ 4,819,000,000	$ 2,107,000,000
Number of employees | employee			103,300	103,300
Percentage of employees represented by various U.S. labor organizations				83.00%
Number of technicians | technician								8
Surety Bonds | United Airlines, Inc.
Commitments and Contingencies [Line Items]
Contingent liabilities based on participation			$ 429,000,000	$ 429,000,000
Tax-Exempt Special Facilities Revenue Bonds
Commitments and Contingencies [Line Items]
Underlying debt and interest			1,900,000,000	1,900,000,000
Tax-Exempt Special Facilities Revenue Bonds | Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Underlying debt and interest			447,000,000	447,000,000
Contingent liabilities based on participation			2,500,000,000	2,500,000,000
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Underlying debt and interest			77,000,000	77,000,000
Floating Rate Debt
Commitments and Contingencies [Line Items]
Long term debt			11,300,000,000	$ 11,300,000,000
Debt instrument, remaining terms				12 years
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms				12 years
Aggregate balance			$ 8,100,000,000	$ 8,100,000,000