Whittle W1 jet propulsion engine at Lutterworth, Leicestershire, 1941.

While still a cadet at Cranwell, Sir Frank Whittle (1907-1996) published a thesis entitled 'Speculation' which put forward the basic thermodynamics for this, the first jet aircraft engine. In March 1938 the Ministry gave Whittle a contract for an engine, and in May 1941 the jet propelled Gloster E28/39 took off from Cranwell. This was the first real proof that jet propulsion was a viable alternative to the propeller. Photograph by Power Jets Ltd.