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Long-Term Debt and Other Borrowings - Additional Information (Detail) $ in Thousands						3 Months Ended	12 Months Ended
	Oct. 01, 2020 USD ($)	Sep. 27, 2019 USD ($)	Sep. 25, 2019 USD ($)	Jun. 14, 2019 USD ($) Air-craft	Jan. 28, 2019 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2020 USD ($)
Debt Instrument [Line Items]
Property and equipment, net							$ 1,212,415	$ 1,273,585
Long-Term Debt							731,724	843,323
Loss on extinguishment of debt								3,616
Payment for debt extinguishment prepayment penalties								1,672
Non-cash lease termination expense								9,540	$ 15,109
Proceeds from long-term debt							23,000	$ 171,658	$ 187,703
Lease payment amount							106,463
Export Development Canada [Member]
Debt Instrument [Line Items]
Principal payments deferred							28,000
Export Development Canada [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of existing aircraft debt	$ 145,000
Repayments of previously deferred principal payments	$ 19,900
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Proceeds from long-term debt							23,000
Equipment Notes [Member]
Debt Instrument [Line Items]
Long-Term Debt							$ 172,100
Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, face amount					$ 91,200
Long term debt interest rate description							LIBOR plus 3.10%
Term loan, term					5 years
Write-off of financing cost					$ 1,900
Payment for debt extinguishment prepayment penalties					1,700
Term Loan [Member] | Spare Engine Facility [Member]
Debt Instrument [Line Items]
Long term debt interest rate description							LIBOR plus 7.25%
Loss on extinguishment of debt					$ 3,600
Term Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate					3.10%
Term Loan [Member] | LIBOR [Member] | Spare Engine Facility [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate					7.25%
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member] | CRJ-700 Aircraft [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 70,000
Long term debt interest rate description							LIBOR plus 5.00%.
Number of aircraft purchased | Air-craft				10
Payment for aircraft purchased				$ 70,000
Non-cash lease termination expense				$ 9,500
Notes Payable to Financial Institution, Collateralized by the Underlying Aircraft, Due 2023 [Member] | LIBOR [Member] | CRJ-700 Aircraft [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate				5.00%
Working Capital Draw Loan [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 35,000
Long term debt interest rate description							one-month LIBOR plus 3.75%.	one-month LIBOR plus 3.75%.
Term loan, term			3 years
Proceeds from long-term debt						$ 23,000	$ 23,000
Working Capital Draw Loan [Member] | LIBOR [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate			3.75%
Aircraft and Equipment [Member] | Pledged as Collateral [Member]
Debt Instrument [Line Items]
Property and equipment, net							$ 1,093,000
Flight Equipment [Member] | Notes Payable to Financial Institution Due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 8,000
Long term debt interest rate description								Libor plus 5.0%.
Flight Equipment [Member] | Notes Payable to Financial Institution Due 2023 [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate		5.00%
RASPRO Aircraft Lease [Member]
Debt Instrument [Line Items]
Lease payment amount										$ 4,000

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