The Gloster E28/39 (G.40) became the first British jet aircraft. The testing of the prototype fitted with a turbojet engine was launched in April 1941. During the final phase of the flight trials in March 1944, the "Pioneer" developed a speed of 755 km/h – the highest speed in the UK at the time. The experimental example of the E28/39 (G.40) was handed over to the Science Museum in London in April 1946. Two prototypes were built.