The Delta 2 was built to investigate the characteristics of flight and control at transonic and supersonic speeds. Two examples were built powered by a Rolls-Royce Avon RA.5 or RA.28 afterburning turbojet engine of 53.4kN and 57.8kN respectively. The first made its maiden flight on 6 October 1954. On 10 March 1956 the RA.5-powered aircraft (flown by Peter Twiss) became the first aircraft to set an over-1,000mph world speed record, with an average of two flights of 1,821km/h. The first aircraft was eventually converted into the BAC 221.