Pilots from the Irish Air Corps helped recreate the live dog-fight scenes, supported by number of civilians, including Charles Boddington and Derek Piggott. Piggott was the only pilot willing to fly beneath the spans of a bridge. Taking the role of both German pilots and with multiple takes from contrasting camera angles, he ended up flying 15 times under the wide span of a bridge in Fermoy, County Cork, Ireland, and 17 times under the narrower span. The two Fokker Dr.I triplane replicas had about four feet (1.3 m) of clearance on each side when passing through the narrower span. He was able to fly through the arch reliably by aligning two scaffolding poles, one in the river and one on the far bank.
The director had placed a flock of sheep next to the bridge so that they would scatter as the plane approached in order to show that the stunt was real and not simulated with models. However, by later takes, the sheep had become accustomed to the planes, and had to be scared by the shepherd instead. In the printed take, the sheep continued to graze, creating a continuity error which can be seen in the finished film.This scene is in the trailer