Sayer joined the Royal Air Force in 1924 but resigned his commission in 1930 to be a test pilot with Hawker Aircraft. In 1934 Hawker took over the Gloster Aircraft Company and Sayer was appointed Chief Test Pilot.
On 21 October 1942 Sayer departed from RAF Acklington in a Hawker Typhoon to carry out tests of a gunsight involving gun firing into Druridge Bay Ranges, he never returned.