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Employee Retirement Plans (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Defined Contribution Plan Disclosure [Line Items] |  |  |
Expense related to matching contributions | $ 71 | $ 69 | $ 65
Eligibility period | 60 days |  |
Frontier 401(k) Plan |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Percent of match | 50.00% |  |
Annual vesting percentage | 25.00% |  |
Vesting period | 4 years |  |
Frontier 401(k) Plan | Maintenance Employee |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contribution, percent of employees' gross pay, initial percentage | 2.00% |  |
Frontier 401(k) Plan | All Employees Excluding Maintenance Employees |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contribution, percent of employees' gross pay, initial percentage | 6.00% |  |
Frontier 401(k) Plan | Flight Attendant |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Percent of match | 100.00% |  |
Employer contribution, percent of employees' gross pay, initial percentage | 6.00% |  |
Frontier 401(k) Plan | Puerto Rico 401(k) Plan |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contribution, percent of employees' gross pay, initial percentage | 6.00% |  |
Frontier Airlines, Inc. Pilots Retirement Plan | Minimum |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Non-elective contribution amount | 12.00% |  |
Frontier Airlines, Inc. Pilots Retirement Plan | Maximum |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Non-elective contribution amount | 15.00% |  |

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- Definition Defined Contribution Plan, Employers Matching Contribution, Eligibility Period + References No definition available. + Details
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 70 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480794/715-70-50-1 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 70 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480794/715-70-50-1 + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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