After Willy Messerschmitt's death in 1978, the former Me 262 pilot Hans Guido Mutke claimed to have exceeded Mach 1 on 9 April 1945 in a Me 262 in a "straight-down" 90° dive. This claim relies solely on Mutke's memory of the incident, which recalls effects other Me 262 pilots observed below the speed of sound at high indicated airspeed, but with no altitude reading required to determine the speed. The pitot tube used to measure airspeed in aircraft can give falsely elevated readings as the pressure builds up inside the tube at high speeds. The Me 262 wing had only a slight sweep, incorporated for trim (center of gravity) reasons and likely would have suffered structural failure due to divergence at high transonic speeds. One airframe—the aforementioned Me 262 V9, Werknummer 130 004, with "Stammkennzeichen" of VI+AD, was prepared as the HG I test airframe with the low-profile "Rennkabine" racing-canopy and may have achieved an unofficial record speed for a turbojet-powered aircraft of , altitude unspecified, even with the recorded wartime airspeed record being set on 6 July 1944, by another Messerschmitt design—the Me 163B V18 rocket fighter setting a record, but landing with a nearly disintegrated rudder surface.