The film was based on the creation of a "mythical" super fighter: the MiG-31 Firefox. The original Firefox from the novel was, cosmetically, nearly identical to the MiG-25. The more intimidating version seen in the movie was created specifically for the film, and takes many of its design cues from the SR-71 Blackbird. In the sequel novel, "Firefox Down," the Firefox's appearance is described as matching the one in the film. For filming, four large-scale replicas were created, along with one full-size model that had dimensions of 66 feet long, 44 feet wide, and 20 feet high. The full-size model was built from a radio station broadcast-antenna skeleton and was capable of taxiing at 30–40 mph.