Summary of Significant Accounting Policies - Summary of Original Cost of Company's Fixed Assets and Accumulated Depreciation or Amortization (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Original Cost	$ 271,491	$ 269,788
Accumulated Depreciation/ Amortization	190,606	169,766
Aircraft
Property, Plant and Equipment [Line Items]
Original Cost	70,779	70,089
Accumulated Depreciation/ Amortization	47,655	40,544
Spare engines
Property, Plant and Equipment [Line Items]
Original Cost	164,706	163,708
Accumulated Depreciation/ Amortization	117,372	103,834
Rotable parts
Property, Plant and Equipment [Line Items]
Original Cost	27,412	27,936
Accumulated Depreciation/ Amortization	18,406	18,655
Ground equipment
Property, Plant and Equipment [Line Items]
Original Cost	2,850	2,718
Accumulated Depreciation/ Amortization	2,217	2,063
Office equipment
Property, Plant and Equipment [Line Items]
Original Cost	4,692	4,519
Accumulated Depreciation/ Amortization	4,331	4,218
Leasehold improvements
Property, Plant and Equipment [Line Items]
Original Cost	1,052	818
Accumulated Depreciation/ Amortization	$ 625	$ 452