The film has two distinct halves: firstly the story of engineer Wallis and his struggle to develop his bouncing bomb, and secondly the story of Gibson and his crew as they train for and then take part in the mission: a bombing raid on the Ruhr dams in Germany, which would cripple German heavy industry. The bombers had to fly extremely low (down to 60 feet) , in order to releae the "bouncing bombs" in a precise timing , so they would hit and burst open the dams.
The flight sequences that take up the last half of the movie were filmed using real Avro Lancaster bombers supplied by the RAF. The aircraft, four Mk. 7s, had to be taken out of storage and specially modified, and cost £130 per hour to run, which amounted to a tenth of the film's costs. (An American cut was made more dramatic by depicting a plane flying into a hill and exploding. This version used stock Warner Brothers footage of a B-17 Flying Fortress as opposed to a Lancaster).
The Upper Derwent Valley in Derbyshire, England (the actual test area for the real raids) doubled as the Ruhr valley for the film.
The flight sequence is heavily quoted in Star Wars (being the basis for the Death Star trench run), and action is often copied scene for scene. Even some dialogue is repeated. Both films require a bomb to be fired at a very specific target with a small window of error.
The scenes with Gibson's black labrador dog, "Nigger", appear in Pink Floyd's The Wall film. These scenes were cut from the ITV's last showing of The Dam Busters after their previous broadcast received complaints for the use of the word nigger. While the ITV has been criticised for censoring historical fact, and maligning the impact of a moving cinematic sequence in the process, the edited showing received many fewer complaints than the previous un-edited broadcast.
The Dam Busters has been praised as one of the greatest war films of all time, but also criticised as glorifying war and destruction.