Factual error: When Jimmy Stewart is almost down to the runway during the bad weather, the aircraft exterior shots show the type of cloud tops found only at high altitude, not low to the ground.
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: Towards the end of the film, the German troops are searching for the marines and cross from the dockside to lighters and then on to a harbour launch. Although this is supposed to be in Bordeaux the launch is marked 'PLA' or Port of London Authority where the action must have been shot.