Goofs

When the Spitfire squadron is returning early in the movie, the "Skipper" is coming in and the markings on the airplane are "SD" "L" ... after he crashes (no flap landing), the markings are "SD" "E" ...

Where David Niven is talking to Leslie Howards' secretary, she is using a 'Royal' typewriter. In a following scene, when Leslie Howard comes out of his office and talks to Crisp (Niven), it appears that the typewriter is a 'Jaydo' or 'Jaybo' brand. In actuality, a closer look reveals that the typewriter in both shots is a Royal, however, during editing, the film was apparently transposed from shot to shot, causing the name of the typewriter to appear differently. This is made clear by looking closely at the telephone on the desk and the clipboard on the wall behind Mitchell's secretary, again, which both have been transposed in the two shots noted.

During the air race in Italy, the Supermarine flown by Niven is an open cockpit while in the air. After the race as Howard is standing by the plane it is shown with an open forward hinged canopy cover.

The Rolls Royce Merlin engine is not named after the character from the King Arthur legends. Rolls Royce named some of its engines after birds of prey, such as Merlin, Peregrine, Kestrel, Goshawk.

During test flight of the plane, a close-up of the cockpit was shown. The type of canopy in the scene is called a "Malcolm Hood" and was not used on early model Spitfires.

At the end of the movie when the spitfire pilots are searching for the enemy planes, one of the pilots uses both hands to attach the face mask. This means he is not holding the joy stick but the plane being uncontrolled doesn't deviate in any way.

During the final fight scenes, the pilots are flying through clouds but no moisture appears on the glass canopy.