Commitments and Contingencies - Aircraft-Related Commitments and Financing Arrangements (Details) $ in Millions	Dec. 31, 2023 USD ($) aircraft aircraftEngine aircraft_engine
Aircraft-Related Secured Debt
Interest Commitments
Interest commitments, 2024	$ 80.2
Interest commitments, 2025	73.6
Interest commitments, 2026	67.3
Interest commitments, 2027	60.2
Interest commitments, 2028	51.7
Interest commitments, 2029 and beyond	$ 204.5
Secured Debt \| 8.00% senior secured notes due in 2025
Interest Commitments
Stated interest rate percentage	8.00%
Non-Aircraft-Related Secured Debt, Unsecured Debt And Convertible Debt
Interest Commitments
Interest commitments, 2024	$ 96.7
Interest commitments, 2025	89.4
Interest commitments, 2026	5.9
Interest commitments, 2027	3.4
Interest commitments, 2028	3.4
Interest commitments, 2029 and beyond	7.1
Aircraft and Related Flight Equipment
Committed Expenditures
Committed expenditures, 2024	507.6
Committed expenditures, 2025	1,018.6
Committed expenditures, 2026	1,034.3
Committed expenditures, 2027	1,100.0
Committed expenditures, 2028	1,035.2
Committed expenditures, 2029 and beyond	923.8
Non-aircraft Related Commitments
Committed Expenditures
Committed expenditures, 2024	65.0
Committed expenditures, 2025	27.5
Committed expenditures, 2026	18.1
Committed expenditures, 2027	18.0
Committed expenditures, 2028	1.9
Committed expenditures, 2029 and beyond	$ 0.0
PurePower PW1100G-JM Engine \| 2029
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of spare aircraft engines ordered \| aircraft_engine	19
A320 and A321
Aircraft Rent Commitments [Abstract]
Number of delivered aircraft with secured debt financing commitments \| aircraftEngine	71
Airbus
Unrecorded Unconditional Purchase Obligation [Line Items]
Future aircraft to be received \| aircraft	99
Airbus \| 2025
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of aircraft with secured debt financing commitments scheduled for delivery \| aircraft	18
Airbus \| 2029
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of aircraft without secured financing commitments scheduled for delivery \| aircraft	81
Third Party Lessor \| A320Neo And A321Neo \| 2025
Unrecorded Unconditional Purchase Obligation [Line Items]
Future aircraft to be received \| aircraftEngine	22
Third Party Lessor \| A320NEO
Aircraft Rent Commitments [Abstract]
Aircraft rent commitments, 2024	$ 72.4
Aircraft rent commitments, 2025	167.8
Aircraft rent commitments, 2026	183.3
Aircraft rent commitments, 2027	183.3
Aircraft rent commitments, 2028	183.3
Aircraft rent commitments, 2029 and beyond	$ 1,409.3

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Number of Spare Aircraft Engines Ordered

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Number of Aircraft with Secured Debt Financing Commitments Scheduled for Delivery

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Contractual interest rate for funds borrowed, under the debt agreement.

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