The first production variant was a fighter designated the "Swift F Mk 1", of which 18 were eventually built. It was powered by a single 7,500 lbf (33.4 kN)-thrust Avon 109 engine and carried an armament of two 30 mm ADEN cannons. On 25 August 1952, the first flight of a production standard Swift F 1 took place. Peter Thorne, who had been appointed as the senior RAF test pilot for the incoming Swift in 1954, came to doubt the aircraft's suitability; observations by Thorne and several other pilots noted the Swift to possess unusual handling qualities alongside a troublesome engine.