Summary of Significant Accounting Policies - Summary of Original Cost of Company's Fixed Assets and Accumulated Depreciation or Amortization (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Property, Plant and Equipment, Excluding Construction in Progress
Property, Plant, and Equipment [Line Items]
Original Cost	$ 253,525	$ 262,158
Accumulated Depreciation/ Amortization	217,193	217,938
Aircraft
Property, Plant, and Equipment [Line Items]
Original Cost	62,362	65,480
Accumulated Depreciation/ Amortization	54,670	55,544
Spare engines
Property, Plant, and Equipment [Line Items]
Original Cost	152,487	157,997
Accumulated Depreciation/ Amortization	134,822	135,278
Rotable parts
Property, Plant, and Equipment [Line Items]
Original Cost	29,805	29,823
Accumulated Depreciation/ Amortization	19,565	19,223
Ground equipment
Property, Plant, and Equipment [Line Items]
Original Cost	2,952	2,953
Accumulated Depreciation/ Amortization	2,597	2,466
Office equipment
Property, Plant, and Equipment [Line Items]
Original Cost	4,782	4,782
Accumulated Depreciation/ Amortization	4,615	4,547
Leasehold improvements
Property, Plant, and Equipment [Line Items]
Original Cost	1,137	1,123
Accumulated Depreciation/ Amortization	$ 924	$ 880