 A total of five Boeing B-17s were obtained for filming.Other U.S. aircraft used are the Consolidated PBY Catalina and, especially, the Curtiss P-40 Warhawk (two flyable examples were used).Predominantly, P-40 fighter aircraft are used to depict the U.S. defenders with a full-scale P-40 used as a template for fiberglass replicas (some with working engines and props) that were strafed and blown up during filming.