Visible crew/equipment: When Fred kisses Peggy, a boom mic is reflected in the left side of the car.
Factual error: Fred would not have been a captain without prior college education. He was previously a soda jerk and would have been enlisted.
Revealing mistake: When Fred Derry gets on the B-17 at the end of the movie to exercise his demons, the nose section of the plane noticeably moves when he gets on and gets off, showing it's a studio prop.