BFW M.21
The Messerschmitt M 21 was a school biplane was constructed from aircraft Messerschmitt and manufactured by the Bavarian Aircraft Works in the late 1920s.
History
The two-seat M 21 was the first biplane of the company and provided a further development of the BFW 3a; they had foldable wings and a fuel tank in the upper wing. Two prototypes were built, which only differed in the engine.