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[Member] Mesa Airlines Inc. Equity Components [Axis] Equity Components [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] BASIS OF PRESENTATION Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Other Performance Measure, Amount Other Performance Measure, Amount Schedule of Estimated Future Payments of Contractual Obligation Contractual Obligation, Fiscal Year Maturity [Table Text Block] Entity Address, State or Province Entity Address, State or Province Frequent Flyer Program Frequent Flyer Program [Member] Frequent Flyer Program [Member] Total current liabilities Liabilities, Current Domestic (U.S. and Canada) Domestic Destination [Member] Interest capitalized Interest Costs Capitalized Adjustment Aircraft maintenance materials and outside repairs Aircraft Maintenance, Materials, and Repairs Individual: Individual [Axis] Azul Azul Linhas Aereas Brasileiras S.A. [Member] Azul Linhas Aereas Brasileiras S.A. 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Equity [Abstract] Equity [Abstract] 2029 Unrecorded Unconditional Purchase Obligation, to be Paid, Year Three Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Current maturities of long-term debt, finance leases, and other financial liabilities Long-Term Debt and Lease Obligation, Current Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Ownership [Domain] Ownership [Domain] Schedule of Components of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Comprehensive Income (Loss) Note [Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] United Airlines, Inc. 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Operating income Operating Income (Loss) Retained earnings Retained Earnings (Accumulated Deficit) Commitments and Contingencies [Line Items] Commitments and Contingencies [Line Items] Commitments And Contingencies [Line Items] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] Share issued for settlement of warrants (in shares) Stock issued for settlement of warrants (in shares) Stock Issued During Period, Shares, Net Share Settlement From Warrants Exercised Stock Issued During Period, Shares, Net Share Settlement From Warrants Exercised Passenger revenue Passenger revenue Passenger [Member] Current Fiscal Year End Date Current Fiscal Year End Date Class of Stock [Axis] Class of Stock [Axis] Other Investments Other Equity Investments [Member] Other Investments Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Miscellaneous, net Other Nonoperating Income (Expense) Statement [Table] Statement [Table] Financing Activities: Financing Activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Percentage of employees represented by various U.S. labor organizations Percentage Of Employees Represented By Labor Organizations Percentage of employees represented by labor organizations Receivables, net Receivables, net Receivables, Net, Current Variable Rate [Domain] Variable Rate [Domain] Beginning Balance Ending Balance Contract with Customer, Liability Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Equity securities Equity Securities, FV-NI, Current Advance ticket sales Contract With Customer, Liability, Current, Advance Ticket Sales Contract With Customer, Liability, Current, Advance Ticket Sales Reconciliation of cash, cash equivalents and restricted cash: Cash and Cash Equivalents [Abstract] Number of aircraft operated Number of Aircraft Operated Property and equipment acquired through the issuance or modification of debt, finance leases and other financial liabilities Noncash Or Part Noncash Acquisition, Fixed Assets Acquired, Net Of Vendor Credits Noncash Or Part Noncash Acquisition, Fixed Assets Acquired, Net Of Vendor Credits Total Unrecorded Unconditional Purchase Obligation All Adjustments to Compensation All Adjustments to Compensation [Member] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Amendment Flag Amendment Flag 2028 Long-Term Debt, Maturity, Year Two Other Postretirement Benefits Other Postretirement Benefits Plan [Member] Revenue From Contract With Customer [Line Items] Revenue From Contract With Customer [Line Items] [Line Items] for Revenue From Contract With Customer [Table] [Table] Stock held in treasury, at cost Treasury Stock, Common, Value 2026 Notes 4.375% Secured Notes Due 2026 [Member] 4.375% Secured Notes Due 2026 Termination Date Trading Arrangement Termination Date Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] 2028 Unrecorded Unconditional Purchase Obligation, to be Paid, Year Two Basic weighted-average shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Distribution expenses Selling Expense Value of authorized shares yet to be purchased under program Share Repurchase Program, Remaining Authorized, Amount Schedule of Computation of Basic and Diluted Earnings (Loss) Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Subscribed equity investments in connection with reorganization process Equity Securities, Restructuring Agreement, Committed Investment Amount Equity Securities, Restructuring Agreement, Maximum Investment Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Nonoperating income (expense): Nonoperating income (expense): Nonoperating Income (Expense) [Abstract] Entity Tax Identification Number Entity Tax Identification Number Operating expense: Operating expense: Costs and Expenses [Abstract] Amounts reclassified to earnings Reclassification from AOCI, Current Period, Tax Amounts reclassified to earnings Reclassification from AOCI, Current Period, before Tax, Attributable to Parent Restructuring and Related Activities [Abstract] Restructuring and Related Activities [Abstract] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common shares, issued (in shares) Common Stock, Shares, Issued 2030 Long-Term Debt, Maturity, Year Four CommuteAir CommuteAir LLC [Member] CommuteAir LLC [Member] UAL And United UAL And United [Member] UAL And United [Member] Interest expense Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Fund United Airlines Ventures Sustainable Flight Fund [Member] United Airlines Ventures Sustainable Flight Fund [Member] Total Shareholder Return Amount Total Shareholder Return Amount Aircraft rent Aircraft Rental Insider Trading Arrangements [Line Items] Security Exchange Name Security Exchange Name Ancillary Services Passenger, Ancillary Fees [Member] Passenger - Ancillary Fees [Member] Last Nine Months of 2026 Long-Term Debt, Maturity, Remainder of Fiscal Year Term Loan Credit and guaranty Agreement Term Loan Due 2024 [Member] Term Loan Due 2024 Travel miles redeemed Travel Miles Redemption, Frequent Flyer Deferred Revenue Travel miles redemption, frequent flyer deferred revenue. Total noncurrent liabilities Liabilities, Noncurrent Other operating revenue Product and Service, Other [Member] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Redemption of aggregate principal amount of outstanding debt Debt Instrument, Repurchased Face Amount Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Other Other Liabilities, Current Asset Class [Domain] Asset Class [Domain] Statement [Line Items] Statement [Line Items] Variable Rate [Axis] Variable Rate [Axis] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Common Stock Common Stock [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Corporate debt Corporate Debt Securities [Member] Net increase in cash, cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation