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 as the design was originally conceived as a short-range interceptor. The E-7 rectified this problem as it was the first Bf 109 subtype to be able to carry a drop tank, usually the standardized Luftwaffe 300 L (80 US gal) capacity unit mounted on a centre-line rack under the fuselage, which increased its range to 1,325 km (820 mi). Alternatively, a bomb could be fitted and the E-7 could be used as a "Jabo" fighter-bomber. Previous Emil subtypes were progressively retrofitted with the necessary fittings for carrying a drop tank from October 1940. Early E-7s were fitted with the 1,100