The most produced military aircraft of all time, the Il-2 started life in 1938 with the design of the TsKB-55 by the team of Sergey Ilyushin. This two seat aircraft incorporated an armoured shell that protected the engine, fuel tank, radiators and crew. To save weight, the armour was a part of the load bearing stucture of the aircraft, but even with this it was overweight. Redesigned as a single seater, and powered with a newer Mikulin AM-38 engine optimised for low altitudes, the Il-2 was accepted into service in March 1941.