Concentrations

12 Months Ended

Sep. 30, 2019

Risks And Uncertainties [Abstract]

Concentrations

4. Concentrations

At September 30, 2019, the Company had capacity purchase agreements with American and United. All of the Company's consolidated revenue for the years ended September 30, 2019, 2018 and 2017 and accounts receivable at the end of September 30, 2019 and 2018 was derived from these agreements. The terms of both the American and United capacity purchase agreements are not aligned with the lease obligations on the aircraft performing services under such agreements. As of September 30, 2019, we had 17 aircraft with leases extending past the term of their corresponding capacity purchase agreements which results in a significant amount of an aggregate exposure and no financing arrangements with projected negativity. We intend to continue to align the terms of our aircraft leases and financing agreements with the terms of our capacity purchase agreements in order to maintain low "tail risk."

Amounts billed by the Company under capacity purchase agreements are subject to the Company's interpretation of the applicable capacity purchase agreement and are subject to audit by the Company's major airline partners. Periodically, the Company's major airline 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 airline partner. As such, the Company periodically reviews amounts past due and records a reserve for amounts estimated to be uncollectible. The allowance for doubtful accounts was $1.0 million and $1.3 million at September 30, 2019 and 2018, respectively. If the Company's ability to collect these receivables and the financial viability of our partners is materially different than estimated, the Company's estimate of the allowance could be materially impacted.

American accounted for approximately 53%, 54% and 56% of the Company's total revenue for the years ended September 30, 2019, 2018 and 2017, respectively. United accounted for approximately 47%, 46% and 44% of the Company's total revenue for the years ended September 30, 2019, 2018 and 2017, respectively. A termination of either the American or the United capacity purchase agreement would have a material adverse effect on the Company's business prospects, financial condition, results of operations, and cash flows.