was a B-17F model, so any B-17Gs used in the film were heavily modified to look like an earlier F model, having chin turrets removed, tail gun positions retrofitted with older designs and being painted olive drab green. During filming, two B-17s portrayed the Belle (one was the movie version of the Memphis Belle (N3703G) and the other was Sally B for scenes requiring pyrotechnics such as smoke and sparks indicating machine gun "hits") while the rest had nose art and squadron markings changed numerous times to make it appear there were more aircraft. Ground sequences for the movie (including takeoff and landing scenes) were filmed at the non-operational RAF Binbrook in Lincolnshire, England with a period control tower and vehicles being placed on site. Flying sequences were flown from the airfield site of the Imperial War Museum Duxford. All the extras for the film were obtained from auditions held in the area and included current and former members of the Royal Air Force. The filmmakers also used Pinewood Studios to shoot interior scenes and to shoot various models of B-17s. A North American B-25 Mitchell was used to film the majority of the aerial scenes with several fixed and trainable cameras also mounted on the available B-17s and fighter aircraft for action shots. A Grumman TBM Avenger (with its tail section painted the same olive drab tones used on the B-17s) was used as back-up for a short time when the B-25 became unserviceable during filming. The film pilots were warbird display pilots coming from the UK, USA, France, Germany, New Zealand and Norway, the roster changing several times as pilots had to return to their full-time jobs during filming. The flying sequences were devised and planned under the coordination of Old Flying Machine Company (OFMC) pilots Ray Hanna and his son Mark, who also acted as chief pilots for the fighter aircraft used and flew the camera-equipped fighter and TBM Avenger aircraft during filming. Due to a shortage of actual B-17 airframes, wooden silhouette mock-ups were made and placed at distant parts of the airfield. Filming accident A French B-17G (F-BEEA), used as a filming platform, hit a tree and a pile of gravel after losing engine power and swinging during takeoff from Binbrook and was destroyed by the subsequent fire. All 10 of the crew escaped with only minor injuries, the most serious of which being a