One April night in 1973, FedEx delivered its first packages. Five years later, the Memphis-based company placed an order for its first Boeing 737.

Now, FedEx and Boeing are building on that nearly four-decade-long relationship.

Boeing and FedEx Express — a subsidiary of FedEx Corp. — announced July 6 they would work together on Boeing’s next iteration of its ecoDemonstrator program.

“Boeing goes through a rigorous selection process to decide which technology to test on an upcoming ecoDemonstrator,”…