The scene where the helicopter lands and then takes off again from a flat wagon on a train traveling at over 40mph had never been attempt before this film and had to be repeated 15 times over two days before the directors were satisfied that it looked just right.
Skysport Engineering was commissioned to build a replica Sopwith Pup which could be suspended from a crane and "flown" and crashed with a stuntman inside for the opening sequences of Biggles's rescue. Attention was given to every detail of its construction so that even when it was burnt the charred remains would look authentic. The wings and frame had to be selectively strengthened and weakened so that it would crumple and break to look as though it has fallen from 1000ft, not 10ft as in reality.
A late 1930's Boeing Stearman and a modified late 1940s Belgian Stampe SV-4 were used to stand in for the WW1 aircraft flown and craft from the Shuttleworth collection added authenticity to the ground sequences.
The helicopter used in the film was a Bell Model 206BII JetRanger, registered G-BAKF with pop-out emergency floats fitted on the skids. Later on, it was involved in a thankfully non-fatal accident in 1989 after colliding with electrical wires when the pilot was preparing to land. The crew escaped with minor injuries, but the helicopter was written off and broken up for spare parts.
The original script called for an adventure film in the mould of Raiders of the Lost Ark (1981) and would have been much more faithful to Johns' original novels. During scriptwriting, however, Back to the Future (1985) was released and became a major hit, so the script was duly altered to follow this trend, in an attempt to capitalise on Back to the Future's popularity.
The trivia item below may give away important plot points.
At the end of the movie when Jim is transported through time to find Biggles and his team captured by native tribesmen in the highlands of New Guinnea the masks the tribesmen are wearing are those of the Asaro Mud Men. The masks are still worn today for religious ceremonies