Concentrations	12 Months Ended
Sep. 30, 2019
Concentrations
Concentrations	2. Concentrations Major Customers and Products In fiscal 2019, 2018 and 2017, the Company derived 53%, 48% and 54%, respectively, of total sales from five customers, although not all the same customers in each year. Accounts receivable and contract assets related to those top five customers was $1.3 million, $1.4 million and $1.3 million as of September 30, 2019, 2018 and 2017, respectively. The largest customer, Pilatus, accounted for 25% of total revenue in fiscal year 2019 and 20% of total revenue in fiscal year 2018. In fiscal year 2017, the three largest customers, Sierra Nevada, Pilatus and DHL accounted for 16%, 12% and 10% of total revenue, respectively. Flat panel sales were 90%, 75% and 89% of total sales in the years ended September 30, 2019, 2018 and 2017, respectively. Sales of air data systems and components were 10%, 25% and 11% of total sales for the years ended September 30, 2019, 2018 and 2017, respectively. Sales to government contractors and agencies accounted for approximately 20%, 32% and 53% of total sales during fiscal years 2019, 2018 and 2017, 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 2019 the Company had two suppliers that accounted for 23.4% of the Company's total inventory related purchases. During fiscal 2018 the Company had one supplier that accounted for 11% 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 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.

2. Concentrations

Major Customers and Products

In fiscal 2019, 2018 and 2017, the Company derived 53%, 48% and 54%, respectively, of total sales from five customers, although not all the same customers in each year. Accounts receivable and contract assets related to those top five customers was $1.3 million, $1.4 million and $1.3 million as of September 30, 2019, 2018 and 2017, respectively.

The largest customer, Pilatus, accounted for 25% of total revenue in fiscal year 2019 and 20% of total revenue in fiscal year 2018. In fiscal year 2017, the three largest customers, Sierra Nevada, Pilatus and DHL accounted for 16%, 12% and 10% of total revenue, respectively.

Flat panel sales were 90%, 75% and 89% of total sales in the years ended September 30, 2019, 2018 and 2017, respectively. Sales of air data systems and components were 10%, 25% and 11% of total sales for the years ended September 30, 2019, 2018 and 2017, respectively. Sales to government contractors and agencies accounted for approximately 20%, 32% and 53% of total sales during fiscal years 2019, 2018 and 2017, 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 2019 the Company had two suppliers that accounted for 23.4% of the Company's total inventory related purchases. During fiscal 2018 the Company had one supplier that accounted for 11% 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 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.