Concentrations	12 Months Ended
Sep. 30, 2018
Concentrations
Concentrations	2. Concentrations Major Customers and Products In fiscal 2018, 2017 and 2016, the Company derived 48%, 54% and 51%, respectively, of total sales from five customers, although not all the same customers in each year. Accounts receivable and unbilled receivables related to those top five customers was $1.4 million, $1.3 million and $1.6 million as of September 30, 2018, 2017 and 2016, respectively. The Company had one customer that accounted for 27% of the Company’s accounts receivable balance as of September 30, 2018. Due to contractual terms with this customer, the amount will not be paid within their normal 45 day payment terms. In fiscal 2018, the largest customer, Pilatus accounted for 20% of total sales. In fiscal 2017, the three largest customers, Sierra Nevada, Pilatus and DHL accounted for 16%, 12% and 10% of total sales, respectively. In fiscal 2016, the three largest customers, Sierra Nevada, Jet2.com and DHL accounted for 13%, 12% and 11% of total sales, respectively. Flat panel sales were 75%, 89% and 95% of total sales in the years ended September 30, 2018, 2017 and 2016, respectively. Sales of air data systems and components were 25%, 11% and 5% of total sales for the years ended September 30, 2018, 2017 and 2016, respectively. Sales to government contractors and agencies accounted for approximately 32%, 53% and 32% of total sales during fiscal years 2018, 2017 and 2016, respectively. The government agency or general contractor typically retains the right to terminate the contract at any time at its convenience. Upon alteration or termination of these contracts, IS&S is typically entitled to an equitable adjustment to the contract price so that it would be compensated for delivered items and allowable costs incurred. Accordingly, because these contracts can be terminated, the Company cannot be assured that its backlog will result in sales. Major Suppliers The Company buys several of its components from sole source suppliers. Although there are a limited number of suppliers of particular components, management believes other suppliers could provide similar components on comparable terms. During fiscal 2018 the Company had one supplier that accounted for 11% of the Company’s total inventory related purchases. During fiscal 2017 the Company had three suppliers that accounted for 33% of the Company’s total inventory related purchases. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash balances and accounts receivable. The Company invests its excess cash where preservation of principal is the major consideration. Cash balances are maintained with two major banks. Balances on deposit with certain money market accounts and operating accounts may exceed the Federal Deposit Insurance Corporation (“FDIC”) limits. The Company’s customer base consists principally of companies within the aviation industry. The Company requests advance payments and/or letters of credit from customers that it considers to be credit risks. The Company recorded a charge for impairment for unbilled receivables in the amount of $3.7 million related to the Delta contract as of September 30, 2014, (See Note 5. Unbilled Receivable in Notes to Consolidated Financial Statements).

2. Concentrations

Major Customers and Products

In fiscal 2018, 2017 and 2016, the Company derived 48%, 54% and 51%, respectively, of total sales from five customers, although not all the same customers in each year. Accounts receivable and unbilled receivables related to those top five customers was $1.4 million, $1.3 million and $1.6 million as of September 30, 2018, 2017 and 2016, respectively.

The Company had one customer that accounted for 27% of the Company’s accounts receivable balance as of September 30, 2018. Due to contractual terms with this customer, the amount will not be paid within their normal 45 day payment terms.

In fiscal 2018, the largest customer, Pilatus accounted for 20% of total sales. In fiscal 2017, the three largest customers, Sierra Nevada, Pilatus and DHL accounted for 16%, 12% and 10% of total sales, respectively. In fiscal 2016, the three largest customers, Sierra Nevada, Jet2.com and DHL accounted for 13%, 12% and 11% of total sales, respectively.

Flat panel sales were 75%, 89% and 95% of total sales in the years ended September 30, 2018, 2017 and 2016, respectively. Sales of air data systems and components were 25%, 11% and 5% of total sales for the years ended September 30, 2018, 2017 and 2016, respectively. Sales to government contractors and agencies accounted for approximately 32%, 53% and 32% of total sales during fiscal years 2018, 2017 and 2016, respectively. The government agency or general contractor typically retains the right to terminate the contract at any time at its convenience. Upon alteration or termination of these contracts, IS&S is typically entitled to an equitable adjustment to the contract price so that it would be compensated for delivered items and allowable costs incurred. Accordingly, because these contracts can be terminated, the Company cannot be assured that its backlog will result in sales.

Major Suppliers

The Company buys several of its components from sole source suppliers. Although there are a limited number of suppliers of particular components, management believes other suppliers could provide similar components on comparable terms.

During fiscal 2018 the Company had one supplier that accounted for 11% of the Company’s total inventory related purchases. During fiscal 2017 the Company had three suppliers that accounted for 33% of the Company’s total inventory related purchases.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash balances and accounts receivable. The Company invests its excess cash where preservation of principal is the major consideration. Cash balances are maintained with two major banks. Balances on deposit with certain money market accounts and operating accounts may exceed the Federal Deposit Insurance Corporation (“FDIC”) limits. The Company’s customer base consists principally of companies within the aviation industry. The Company requests advance payments and/or letters of credit from customers that it considers to be credit risks.

The Company recorded a charge for impairment for unbilled receivables in the amount of $3.7 million related to the Delta contract as of September 30, 2014, (See Note 5. Unbilled Receivable in Notes to Consolidated Financial Statements).