The Messerschmitt Bf 109 is a monoplane fighter aircraft that was designed and initially produced by the German aircraft manufacturer Bayerische Flugzeugwerke (BFW). Together with the Focke-Wulf Fw 190, the Bf 109 formed the backbone of the Luftwaffe's fighter force during the Second World War. It was commonly called the Me 109 by Allied aircrew and some German aces/pilots, even though this was not the official model designation.