the straight-winged American jets and piston-engined fighters initially deployed during the Korean War. The MiG-15 is believed to have been one of the most produced jet aircraft; in excess of 13,000 would ultimately be manufactured. The MiG-15, which could not safely exceed Mach 0.92, served as the basis for the MiG-17, which was designed to be controllable at higher Mach numbers. Its wing sweep, 45° near the fuselage ( the same as the F-100 Super Sabre), changed to 42° for the outboard part of the wing. A further derivative of the design, designated MiG-19, featured a relatively thin wing suited to supersonic flight that was designed at TsAGI, the Soviet Central Aerohydrodynamic Institute; swept back at an angle of 55 degrees, this wing featured a single wing fence on each side. A specialist high-altitude variant, the Mig-19SV, featured, amongst other changes, an adjustable flap to generate greater lift at higher altitudes, helping to increase the aircraft's ceiling from to . Germany's swept wing research was also obtained by the Swedish aircraft manufacturer SAAB, with the help of ex-Messerschmitt engineers that had fled to Switzerland during late 1945. At the time, SAAB saw the need to make aeronautical advances, particularly in the new field of jet propulsion. The company incorporated both the jet engine and the swept wing to produce the Saab 29 Tunnan fighter; on 1 September 1948, the first prototype conducted its maiden flight, flown by the English test pilot S/L Robert A. 'Bob' Moore, DFC and bar, Although not well known outside Sweden, the Tunnan was the first Western European fighter to be introduced with such a wing configuration. In parallel, SAAB also developed another swept wing aircraft, the Saab 32 Lansen, primarily to serve as Sweden's standard attack aircraft. Its wing, which had a 10 per cent laminar profile and a 35° sweep, featured triangular fences near the wing roots in order to improve airflow when the aircraft was being flown at a high angle of attack. On 25 October 1953, a SAAB 32 Lansen attained a Mach number of at least 1.12 while in a shallow dive, exceeding the sound barrier. The successes of aircraft such as the Hawker Hunter, the B-47, and F-86 showed the value of the swept wing research acquired from Germany. Eventually, almost all advanced design efforts for high speed aircraft would incorporate a wing with a swept leading edge, with either