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Summary of Significant Accounting Policies - Additional Information (Detail)
 3 Months Ended
Dec. 31, 2024
USD ($)
AirCraft
Dec. 31, 2023
USD ($)
Sep. 30, 2024
USD ($)
Summary Of Significant Accounting Policies [Line Items]      
Deferred revenue $ 5,600,000    
Lease revenue $ 20,200,000 $ 34,900,000  
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration] Revenue From Contract With Customer Excluding Assessed Tax Revenue From Contract With Customer Excluding Assessed Tax  
Finance leases $ 0    
Number of air craft leased from third parties | AirCraft 5    
Current and non-current deferred credit contract liability balances $ 3,100,000   $ 4,100,000
Recognized deferred credits within contract revenue 1,000,000 $ 1,000,000  
Amortization of heavy maintenance and major overhaul costs charged to depreciation and amortization expense 1,100,000 800,000  
Deferred heavy maintenance balance, net of accumulated amortization 5,400,000   $ 6,400,000
Engine overhaul expense 10,100,000 5,800,000  
Engine overhaul pass-through expense 10,100,000 5,700,000  
Airframe check expense 8,400,000 6,400,000  
Airframe check pass-through expense $ 7,700,000 $ 3,800,000