During the Stuka attack on the radar station, the two Stuka radio controlled models that collide was a complete accident. It looked good so was left in the final version.

During the scenes dealing with the dive bomber attacks on the RAF radar stations, the filmmakers used rather un-convincing radio-controlled models to portray the German Ju87 Stukas. Originally, the producers had intended to use Proctor trainers, modified to resemble the Stuka. However the British aviation authorities refused to pass them as airworthy, forcing the producers to resort to using the models.