Factual error: One of the shots of individual British Lancaster bombers approaching one of the dams is actually and incorrectly an American B17, seen for only a second or two. [At no time in the film is a B17 visible in the British release of the film. However the B17 crashing appears in a version of the film released in the U.S.A.]
Factual error: When belts of ammunition are being loaded into the rear of a Lancaster before the mission they appear to be 20mm or .50 cal. The Brownings on Lancaster were 0.303.