Murder in the Clouds (1934)

Bob "three star" is the hotshot pilot for Trans America Lines. When he is not flying for the airlines, he can get into trouble doing aerobatics over the field. His main squeeze is Judy Wagner, a stewardess for the airlines. Tom Wagner, her younger brother has just started flying for the line. Tom and Bob are to fly on a secret mission to carry a scientist with a new high explosive mixture to Washington. Unfortunately, Jason, secretary to Mr. Lackey, is working for a secret foreign power and hears about the flight. This causes Bob to get jumped before the flight so another pilot, George, volunteers to take Bob's place. When the plane explodes in flight, there is a race between government agents to get the mixture back and the bad guys to get the mixture out of the country.