Concentrations of Credit Risk	3 Months Ended
Dec. 31, 2022
Risks And Uncertainties [Abstract]
Concentrations of Credit Risk	4. Concentrations of Credit Risk Financial instruments that potentially expose the Company to a concentration of credit risk consist principally of cash and cash equivalents that are primarily held by financial institutions in the United States and accounts receivable. Amounts on deposit with a financial institution may at times exceed federally insured limits. We maintain our cash accounts with high credit quality financial institutions and, accordingly, minimal credit risk exists with respect to the financial institutions. As of December 31, 2022, we had $3.3 million in restricted cash. We have an agreement with a financial institution for a letter of credit facility and to issue letters of credit for particular airport authorities, worker's compensation insurance, property and casualty insurance and other business needs as required in certain lease agreements. Pursuant to the terms of this agreement, $3.3 million of outstanding letters of credit are required to be collateralized by amounts on deposit. Significant customers are those which represent more than 10% of our total revenue or net accounts receivable balance at each respective balance sheet date. All of our revenue for the three months ended December 31, 2022 and 2021 was derived from the American and United CPAs, DHL FSA, and from leases of our CRJ-700 aircraft to GoJet. Substantially all of our accounts receivable at December 31, 2022 and September 30, 2022 was derived from these agreements. American accounted for approximately 45% and 45% of our total revenue for the three months ended December 31, 2022 and 2021, respectively. United accounted for approximately 50% and 49% of our total revenue for the three months ended December 31, 2022 and 2021, respectively. In December 2022, the Company entered into the AA Amendment that provides for the termination and wind-down of the American CPA by April 3, 2023. Also in December 2022, the Company entered into the Amended and Restated United CPA, which transitions the aircraft previously operated under the American CPA to be operated under the Amended and Restated United CPA as of April 2023, refer to Note 1 for further discussion regarding both amendments. A termination of the United CPA would have a material adverse effect on our business prospects, financial condition, results of operations, and cash flows. Amounts billed under our agreements are subject to our interpretation of the applicable agreement and are subject to audit by our major partners. Periodically, our major partners dispute amounts billed and pay amounts less than the amount billed. Ultimate collection of the remaining amounts not only depends upon the Company prevailing under the applicable audit, but also upon the financial well-being of the major partner. As such, we review amounts due based on historical collection trends, the financial condition of the major partners, and current external market factors and record a reserve for amounts estimated to be uncollectible in accordance with the applicable guidance for expected credit losses. Our allowance for doubtful accounts was not material as of December 31, 2022 or September 30, 2022. If our ability to collect these receivables and the financial viability of our major partners is materially different than estimated, our estimate of the allowance for credit losses could be materially impacted.

Concentrations of Credit Risk

3 Months Ended

Dec. 31, 2022

Financial instruments that potentially expose the Company to a concentration of credit risk consist principally of cash and cash equivalents that are primarily held by financial institutions in the United States and accounts receivable. Amounts on deposit with a financial institution may at times exceed federally insured limits. We maintain our cash accounts with high credit quality financial institutions and, accordingly, minimal credit risk exists with respect to the financial institutions.

As of December 31, 2022, we had $3.3 million in restricted cash. We have an agreement with a financial institution for a letter of credit facility and to issue letters of credit for particular airport authorities, worker's compensation insurance, property and casualty insurance and other business needs as required in certain lease agreements. Pursuant to the terms of this agreement, $3.3 million of outstanding letters of credit are required to be collateralized by amounts on deposit.

Significant customers are those which represent more than 10% of our total revenue or net accounts receivable balance at each respective balance sheet date. All of our revenue for the three months ended December 31, 2022 and 2021 was derived from the American and United CPAs, DHL FSA, and from leases of our CRJ-700 aircraft to GoJet. Substantially all of our accounts receivable at December 31, 2022 and September 30, 2022 was derived from these agreements.

American accounted for approximately 45% and 45% of our total revenue for the three months ended December 31, 2022 and 2021, respectively. United accounted for approximately 50% and 49% of our total revenue for the three months ended December 31, 2022 and 2021, respectively. In December 2022, the Company entered into the AA Amendment that provides for the termination and wind-down of the American CPA by April 3, 2023. Also in December 2022, the Company entered into the Amended and Restated United CPA, which transitions the aircraft previously operated under the American CPA to be operated under the Amended and Restated United CPA as of April 2023, refer to Note 1 for further discussion regarding both amendments. A termination of the United CPA would have a material adverse effect on our business prospects, financial condition, results of operations, and cash flows.

Amounts billed under our agreements are subject to our interpretation of the applicable agreement and are subject to audit by our major partners. Periodically, our major partners dispute amounts billed and pay amounts less than the amount billed. Ultimate collection of the remaining amounts not only depends upon the Company prevailing under the applicable audit, but also upon the financial well-being of the major partner. As such, we review amounts due based on historical collection trends, the financial condition of the major partners, and current external market factors and record a reserve for amounts estimated to be uncollectible in accordance with the applicable guidance for expected credit losses. Our allowance for doubtful accounts was not material as of December 31, 2022 or September 30, 2022. If our ability to collect these receivables and the financial viability of our major partners is materially different than estimated, our estimate of the allowance for credit losses could be materially impacted.