Unbilled Receivables	12 Months Ended
Sep. 30, 2018
Unbilled Receivables
Unbilled Receivables	5. Unbilled Receivables Unbilled receivables principally represent sales recorded under the percentage-of-completion method of accounting that have not been billed to customers in accordance with applicable contract terms. Unbilled receivables were $0 and $1.5 million at September 30, 2018 and 2017, respectively. On February 23, 2017 the Company entered into a settlement agreement with Delta. Under the terms of the settlement, Delta paid the Company $7.75 million resulting in the reversal of the $3.6 million reserve and the collection of the unbilled receivable in the fiscal year ended September 30, 2017. The reversal of the reserve is reflected in the selling, general and administrative expenses in the Consolidated Statements of Operations in the fiscal year ended September 30, 2017. The remainder of the amount paid to the Company, approximately $4.1 million is reflected in other income in the fiscal year ended September 30, 2017. The percentage-of-completion method of accounting for EDC revenue, requires estimates of profit margins for contracts be reviewed by the Company on a quarterly basis. If the initial estimates of revenues and costs under a contract are accurate, the percentage-of-completion method results in the profit margin being recorded evenly as revenue is recognized under the contract. Changes in these underlying estimates because of revisions in revenue and cost estimates or the exercise of contract options may result in profit margins being recognized unevenly over a contract because such changes are accounted for on a cumulative basis in the period in which the estimates are revised. Significant changes in estimates related to accounting for long-term contracts may have a material effect on the Company’s results of operations in the period in which the revised estimates are made. Net cumulative catch-up adjustments resulting from changes in estimates increased operating income by $0 and $61,000 during the fiscal years ended September 30, 2018 and 2017, respectively, and reduced operating income by $58,000 during the fiscal year ended September 30, 2016.

5. Unbilled Receivables

Unbilled receivables principally represent sales recorded under the percentage-of-completion method of accounting that have not been billed to customers in accordance with applicable contract terms. Unbilled receivables were $0 and $1.5 million at September 30, 2018 and 2017, respectively. On February 23, 2017 the Company entered into a settlement agreement with Delta. Under the terms of the settlement, Delta paid the Company $7.75 million resulting in the reversal of the $3.6 million reserve and the collection of the unbilled receivable in the fiscal year ended September 30, 2017. The reversal of the reserve is reflected in the selling, general and administrative expenses in the Consolidated Statements of Operations in the fiscal year ended September 30, 2017. The remainder of the amount paid to the Company, approximately $4.1 million is reflected in other income in the fiscal year ended September 30, 2017.

The percentage-of-completion method of accounting for EDC revenue, requires estimates of profit margins for contracts be reviewed by the Company on a quarterly basis. If the initial estimates of revenues and costs under a contract are accurate, the percentage-of-completion method results in the profit margin being recorded evenly as revenue is recognized under the contract. Changes in these underlying estimates because of revisions in revenue and cost estimates or the exercise of contract options may result in profit margins being recognized unevenly over a contract because such changes are accounted for on a cumulative basis in the period in which the estimates are revised. Significant changes in estimates related to accounting for long-term contracts may have a material effect on the Company’s results of operations in the period in which the revised estimates are made. Net cumulative catch-up adjustments resulting from changes in estimates increased operating income by $0 and $61,000 during the fiscal years ended September 30, 2018 and 2017, respectively, and reduced operating income by $58,000 during the fiscal year ended September 30, 2016.