By the end of the 1940s BMW had returned to motorcycle manufacture but still had not restarted automobile manufacture. There were several approaches considered regarding how to re-enter the automotive market. Kurt Donath, technical director of BMW and general manager of the Milbertshofen factory, advocated to produce another manufacturer's old models under licence, also purchasing the tooling to produce the cars from the other manufacturer. Chief engineer Alfred Böning's preferred approach was a small economy car, and he developed the BMW 331 prototype, powered by a motorcycle engine. In the end, it was sales director Hanns Grewenig's proposal that was successful. Grewenig believed that BMW's small production capacity was best suited to luxury cars with high profit margins, similar to the cars BMW made just before the war. To this end, he had Böning and his team design the BMW 501 luxury sedan. The 501 was unveiled in 1951, however delays in receiving and setting up equipment caused production of the 501 to be delayed until late 1952.