The Messerschmitt Me 163 Komet,[N 1] designed by Alexander Lippisch, was a German rocket-powered fighter aircraft. It is the only rocket-powered fighter aircraft ever to have been operational. Its design was revolutionary, and the Me 163 was capable of performance unrivaled at the time. Messerschmitt test pilot Rudy Opitz in 1944 reached 1,123 km/h (698 mph). Over 300 aircraft were built; however, the Komet proved ineffective as a fighter, having been responsible for the destruction of only about nine Allied aircraft (16 air victories for 10 losses, according to other sources).