The Messershmitt Bf 109 is a German World War II fighter that was, along with the Focke Wulf FW 190, the back bone of the Luftwaffe's fighter force. The Bf 109 first saw service in 1937 and was still in service at the dawn of the Jet Age in the end of World War II in 1945. It was one of the most advanced fighters of the era, including such features as all-metal monocoque construction, a closed canopy, and retractable landing gear. It was powered by a liquid cooled, inverted Aero-Engine and a strong prop. From the end of 1941, the Bf 109 steadily being supplemented by the Focke Wolf FW 190. It was commonly called the ME 109, often by Allied aircrew and among German Aces, even though it was not the official German Designation.