The Mitsubishi G4M was a twin-engine, land-based medium bomber manufactured by the Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries, and operated by the Air Service (IJNAS) of the Imperial Japanese Navy from 1940 to 1945. Its official designation was Mitsubishi Navy Type 1 attack bomber and was commonly referred to by Japanese Navy pilots as "Hamaki" due to the cylindrical shape of its fuselage and its tendency to ignite after a hit. The Allied reporting name was "Betty".