Messerschmitt Bf 109 11 July 1938 when Erhard Milch finally allowed Willy Messerschmitt to acquire the company. All Messerschmitt aircraft that originated after that date, such as the Me 210, were to carry the "Me" designation. Despite regulations by the RLM, wartime documents from Messerschmitt AG, RLM and "Luftwaffe" loss and strength reports continued to use both designations, sometimes even on the same page. All extant airframes bear the official "Bf 109" designation on their identification plates, including the final K-4 models. The aircraft was often referred to by the folk-designation, 'Me 109', particularly by the Allies. The aircraft was often nicknamed "Messer"
Messerschmitt Bf 109 variants was identical to the V8, except for its Jumo 210G engine. The V10, V11, V12 and V13 prototypes were built using Bf 109B airframes, and tested the DB 600A engine with the hope of increasing the performance of the aircraft. The DB 600A was dropped as the improved DB601A with direct fuel injection was soon to become available. Developed from the V10 and V13 prototypes, the Bf 109D was the standard version of the Bf 109 in service with the "Luftwaffe" just before the start of World War II. Despite this, the type saw only limited service during the war,