Permission was granted to the producers to use the Royal Air Force Museum's Junkers Ju 87 "Stuka" dive-bomber (one of only two that survive intact). The 1943 aircraft was repainted and slightly modified to resemble a 1940 model Ju 87. The engine was found to be in excellent condition and there was little difficulty in starting it, but returning the aircraft to airworthiness was ultimately too costly for the filmmakers. Instead, two Percival Proctor training aircraft were converted into half-scale "Stukas", with a cranked wing, as "Proctukas" though, in the film, they were not used on-screen. Instead, to duplicate the steep dive of Ju 87 attacks, large models were flown by radio control.