The BMW Logo
The myth of the logo's propellers
The brand mark of the Bayerische Motoren Werke (Bavarian Motor Factories) was designed in the colours of the province Bavaria, according to the first part of the company name.
The black border which delimits the logo dates from the predecessor company, "Rapp Motorenwerke GmbH", from which BMW eventually emerged. The four white and blue propeller-like pieces in the logo's center were included in 1929 to underline BMW's expertise in aircraft engine engineering.
Current information from the BMW company archive denies these statements. According to this, it's just a myth and has noting to do with the true origin of the logo. However, the facts of the case wasn't known in the company itself.
More information:
The history of the BMW logo, by Dr. Florian Triebel - BMW Archive (german)