In reply to Trangia:
From Wikipedia:
The flight sequences of the film were shot using real Avro Lancaster bombers supplied by the RAF. The aircraft, four of the final production B.VIIs, had to be taken out of storage and specially modified by removing the mid-upper gun turrets to mimic 617 Squadron's special aircraft, and cost £130 per hour to run, which amounted to a tenth of the film's costs. A number of Avro Lincoln bombers were also used as "set dressing."
Don't think you could fly a Cessna for £130 per hour these days!
Post edited at 08:11