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Balance Sheet Information - Summary of Certain Significant Amounts Included in Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands | Jun. 30, 2025 | Sep. 30, 2024
--- | --- | ---
Expendable parts and supplies, net: |  |
Expendable parts and supplies | $ 23,441 | $ 39,089
Less: expendable parts warranty | (4,355) | (6,079)
Less: obsolescence | (2,914) | (4,738)
Expendable parts and supplies, net | 16,172 | 28,272
Property and equipment, net: |  |
Property and equipment-gross | 59,692 | 600,924
Less: accumulated depreciation | (27,842) | (174,573)
Property and equipment-net | 31,850 | 426,351
Property and equipment, net | 31,850 | 426,351
Other assets: |  |
Investments in equity securities | 350 | 300
Lease incentives |  | 812
Contract asset | 4,441 | 6,081
Other | 675 | 516
Other assets | 5,466 | 7,709
Other accrued expenses: |  |
Accrued property taxes | 2,483 | 4,650
Accrued interest | 1,029 | 2,997
Accrued vacation | 6,497 | 7,421
Accrued lodging | 4,092 | 4,433
Accrued maintenance | 1,415 | 2,493
Accrued employee benefits | 1,550 | 1,075
Accrued fleet operating expense | 412 | 2,751
Other | 5,537 | 6,488
Other accrued expenses | 23,015 | 32,308
Other noncurrent liabilities: |  |
Warrant liabilities | 100 | 25,225
Lease incentive obligations |  | 1,050
Long-term employee benefits | 1,737 | 485
Other |  | 1,819
Other noncurrent liabilities | 1,837 | 28,579
Aircraft and Other Flight Equipment [Member] |  |
Property and equipment, net: |  |
Property and equipment-gross | 50,104 | 591,421
Other Machinery and Equipment [Member] |  |
Property and equipment, net: |  |
Property and equipment-gross | $ 9,588 | $ 9,503

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