1945 enabled Petter to recruit and expand his team. He recruited Dai Ellis and Ray Creasey in 1946 as his aerodyamicists. He recruited Roland Beamont in May 1947 as his chief experimental test pilot; doing this as a means of bypassing Arthur Sheffield's control of the production test pilots and also because both he and Page wanted close integration of the test pilot within the design team. Members of the team Petter put together to develop the Canberra would go on to lead military aircraft development in the U.K for the next four decades, playing significant roles in the development of the Lightning, TSR-2, Jaguar, and the Tornado, some becoming members of the divisional board of directors. Of this time at Warton, Beamont said "although Petter was generally thought to be difficult I found him logical and 'ahead of the game' and totally oriented on making an enormous success of the Canberra. That it achieved this was due to his personal ability to recognise the technical argument and act on it correctly." The aircraft would stay in operation in the RAF for 57 years until June 2006. In the United States, the Martin Company built the design under licence from 1953, as the Martin B-57, which was operated by the United States Air Force (USAF), NASA, the Pakistan Air Force and Taiwan Air Force. While the type was retired by the USAF in 1983, NASA still operates three. Lightning Despite the lack of enthusiasm for manned supersonic flight in postwar Britain (The Miles M.52 was cancelled in February 1946), Petter made provisional sketches for a supersonic fighter in 1946. To achieve a small frontal area and reduce wave drag it had two Rolls-Royce Derwent engines mounted one above the other in the fuselage, echoing his earlier Westland P13 proposal. He lobbied Whitehall on the matter of supersonic flight and in 1948 Handel Davis and a party from the MoS visited Petter in Warton to discuss experimental supersonic development work under specification E.R. 103. This meeting resulted in Petter initiating a design proposal with Page leading the design and Ray Creasey responsible for the aerodynamics. By July 1948 their proposal incorporated the stacked engine configuration and a high-mounted tailplane but was designed for Mach 1.5. As a consequence it had a conventional 40° degree swept wing This proposal was submitted in the November and in January 1949 the project was designated