In the film, a large white triangle with a black "A" inside it is painted on the vertical stabilizers (tail fins) of the 918th Bomb Group's B-17 airplanes. At the point in World War II depicted in the film, 8th Air Force B-17's did not yet bear these markings, carrying only the plane's serial number on the tail. The white triangle with a black "A" was the identifying insignia for the real-life 91st Bomb Group later in the war. The aircraft used in the movie were marked to match wartime combat camera footage, some of which featured 91st Bomb Group planes.
Insignia incorrect for the period. The Schweinfurt ball bearing plant raids took place in 1943. By that time, the national insignia had the bars on each side of the round star background. Apparently the older star-on-blue with no bars was used to match documentary footage inserted into the movie.
During the Ball Bearing mission, the Picadilly Lilly is shown to have 6 bombs painted under the cockpit (indicating 6 missions). However, a much earlier mission also shows 6 bombs. There were obviously many missions between these 2 shots.
When General Savage visits Lt Col Gately in the hospital, close-up shots are taken from the left side of Gately's bed and long distance shots are taken from the right. The lighting on Gately's face is significantly brighter in the close-ups.
In the wonderful opening shot, LONDON 1949 is framed by a glass door of the Hat shop. As it opens and Dean Jagger exits, a camera and technician are absolutely clearly reflected in the glass swinging away to one side.
During the bombing mission depicted in the film, the tail gun of General Savage's "Picadilly Lily" B-17F airplane is shown briefly, but it is a late-war model "Cheyenne"-type tail turret - incorrect for the time period during which the events in the film take place.
In the movie credits, the flight surgeon is listed as "Capt. 'Doc' Kaiser". However, from the character's first appearance at the crash-landed B-17 in the opening scene, he wears oak leaves of a major (or a lieutenant colonel, since in a B&W movie we can't initially tell if they are gold or silver). Later, he is always referred to as a major.
On the ball bearing bombing mission the camera shows a close up of the exterior of the cockpits of Picadilly Lilly, Reluctant Dragon and Fluffy Fuzzy. All shots show each plane's nose art above the navigator's windows to identify the different planes and crews. Actual nose art was painted below the navigator's windows.
During the first attack on the ball bearing plant, when the bombs are released, you see two groups of bombs on the racks, one in front of the other. The B-17 carried all its bombs in one vertical stack. The American bomber in use at the time that would have had forward and aft stacks would be the B-24. The bomb bay doors on the B-24 roll up like garage doors, but you clearly see the doors hinged back, and the bombs have a round support around the fin. The American bombs of this time had a square support to the fins. The bomb release is shown from what appears to be an Avro Lancaster, a British bomber.
During the aerial combat scenes of the movie's last mission, actual WWII combat footage is randomly inserted to add realism. However, three of these clips clearly show a closeup of an American P-47 fighter attacking the B-17's.
Stock combat footage of air-to-air combat is used extensively. Some clips have been flipped left to right and reused. Others, particularly of German fighters blowing up, were not filmed from bombers but were taken from the gun cameras of Allied fighters, which did not accompany the bombers at this time. (Some shots taken from non-bombers are from cameras on German fighters, on footage captured after the war.)
On the last mission General Savage goes on, right after take-off, the camera slowly zooms in on Piccadilly Lily's cockpit. A minute later the camera zooms in on Reluctant Dragon's cockpit, then Fluffy Fuzz's cockpit. All three times the plane in the background is the same #23613 and the stains and dirt on the roof of the three cockpits is the same.