the mystery of the BMW blue and white logo... what is the source?

In the movie Finding Forrester http://www.imdb.com/title/tt0181536/ Sean Connery is the main character and teaches a young guy a lot, but specifically tells the guy what the blue and white badge was representing the blue sky and the white of a airplane propeller, because of BMW's airplane motors. Good movie by the way

This month's Automobile magazine has a pop quiz and says that is a mistake, and the real reason is the the flag of the Free State of Bavaria was a blue and white flag

So I tried to see what the internet had to say, it's the propeller according to http://www.etiziano.com/I_love_logo_design/secret_of_the_bmw_logo.html

Aircraft engines are the origin of the myth. People think that the BMW logo is based on a rotating airscrew. The origin of this interpretation is the cover of a BMW aircraft magazine. This picture (shown below) was taken in 1929, years after the logo first came into existence. Respect for the publicity department back then for the fact that the airscrew myth continues today. according to http://www.logodesignlove.com/bmw-logo-evolution who asked the BMW Group historian BMW chose the Bavarian national colours as a symbol, 

So it all depends on who you ask