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.]
Trivia: A (corrected) entry states that a USAAF B-17 'Flying Fortress' bomber is visible in the film. In fact in some prints produced for release in the US irrelevant stock footage of a B17 was randomly cut into the film to make it more acceptable to American audiences. This was a deliberate alteration of the film done very much against the wishes of the producer and director, and it explains the 'error' - the contributor has seen one of the non-canon US prints.
Official, Ministry of Aircraft Production: You say you need a Wellington Bomber for test drops. They're worth their weight in gold. Do you really think the authorities will lend you one? What possible argument could I put forward to get you a Wellington?
Doctor B. N. Wallis, C.B.E., F.R.S.: Well, if you told them I designed it, do you think that might help?