The BMW logo is symbolic of a white propeller blade, against a blue sky. It reflects the origins of BMW as a maker of military aircraft engines during the first world war. It is a good example of a strong brand-led company retaining the best of its heritage in the form a of distinctive logo design, without placing too much emphasis on the origins of the logo itself. Bayerische Flugzeugwerke (BFW) is founded on 7th March 1916 and incorporates Otto-Werke. BMW acquires the BFW plant in 1922, but Bayerische Motoren Werke continues to date its foundation from the founding of BFW. On 21st July 1917, Rapp-Motorenwerke is renamed Bayerische Motoren Werke GmbH. The ongoing war means that the small company grows quickly. With expansion in mind, the firm builds a spacious plant right next to the Oberwiesenfeld airfield in Munich and continues to build engines for army planes until 1918. BMW buys the Eisenach automobile plant, where the Austin Seven was successfully produced under the name "Dixi 3/15 PS". This vehicle is developed further, going on sale in 1929 as the BMW 3/15 PS DA 2 with a range of different body shells. A small car with a lot of appeal, its popularity helps the company to survive the lean years of the Depression.