Developed in 1938, the Messerschmitt Me 262 "Schwalbe," ("Swallow") was the world's first operational turbojet aircraft. First flown as a pure jet on July 18, 1942, it proved much faster than conventional airplanes. Development problems, Allied bombings, and cautious Luftwaffe leadership contributed to delays in quantity production. In late 1943, Adolf Hitler agreed to mass production, but insisted the aircraft be used primarily as a fighter-bomber. On July 25, 1944, an Me 262 became the first jet airplane used in combat when it attacked a British photo-reconnaissance Mosquito flying over Munich. As a fighter, the German jet scored heavily against allied bomber formations. The bombers, however, destroyed hundreds of Me 262s on the ground. More than 1,400 Me 262s were produced, but fewer than 300 saw combat. Most remained on the ground awaiting conversion to bombers, or were unable to fly because of lack of fuel, spare parts, or trained pilots.