The second picture shows the three Lancasters used in the film flying together probably for the last time. This was taken at a Battle of Britain Day tribute in Cumbria. The caption on the reverse says that this was taken at Silloth, but in Jonathan Falconer’s Filming the Dam Busters, this is mentioned as taking place at nearby Anthorn. (If anyone can confirm which airfield this is, please let me know. Cumbria resident Dom Howard reckons that it is Silloth– see this link .)
Note in the picture that only two of the aircraft have been modified to the “Dambuster” configuration. The central one must be NX782, which was left as standard and used in an early sequence where Gibson is completing his final flight as CO of 106 Squadron.
Note also how low the three Lancasters are flying, and how close they are to the members of the public wandering across the runway. Modern air displays have much stricter health and safety rules!
Source:
http://dambustersblog.com/category/avro-lancaster/