Jet aircraft development in Europe and the USA had begun as early as the mid-1930s. British and German scientists and aircraft designers were ahead of the field in this respect. The world's first turbojet-powered aircraft, the Heinkel He 178 proof-of-concept aircraft, took to the air on 24th August 1939. The He 178 was intended for verifying the Heinkel HeS 1 centrifugal-flow turbojet. Its cantilever high-wing layout with a retractable tailwheel undercarriage was markedly different from that of the first British jet, the Gloster G.40; this low-wing monoplane with a tricycle landing gear first flew in May 1942. The USA joined the 'jet club' on 1 st October 1942 when the Bell XP-59A Airacomet twinjet fighter made its maiden flight. Soon enough jet engines found their way to production aircraft, both fighters and bombers. The first series-produced jet bomber was the Arado Ar 234 Blitz (Lightning) strike aircraft. The Ar234 V1 prototype, which first flew on 15th June 1943, and the subsequent seven prototypes used a jettisonable take-off dolly, landing on three retractable skids under the fuselage and the engine nacelles; later prototypes and the production version, however, featured a conventional tricycle undercarriage retracting into the fuselage.
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