At least in the original film the aircraft were Lancasters flown by RAF crews; the Technical Advisor was Sqn Ldr HB (Micky) Martin DSO DFC & Bar and the Actor who played Wg Cdr Gibson was (in WW2) Lt R Todd MC (7th Battalion Parachute Regt) who, on D Day, was the first to arrive with his platoon at Pegasus Bridge in support of the Glider borne Troops of the Ox & Bucks Light Infantry.
Now, where do you find a team who would have one tenth of one percent of the actual WW2 knowledge of that team?