 Filming the finale scene with the rail ship was initially delayed because it could not be hoisted onto the track due to large waves caused by the hurricane. The scene was filmed using 14 cameras, with the rail ship traveling 50 feet (15 m) at a time into the set, with debris from the destruction cleared between each take. The ship was powered by four diesel engines and pulled by a large chain at a speed of 18 miles per hour (29 km / h). The three planned collisions in the scene were aided by explosives and hydraulics to ensure the set's structures collapsed precisely. Concrete was also removed from the buildings and replaced with sand-coated balsa wood so the buildings would "crumble" more effectively after being hit by the rail ship. In the scene's final shot, the ship had to stop within a 6-inch (15 cm) area, and was completely successful on the first take. The five-minute scene cost $ 25 million to produce, roughly one quarter of the film's entire budget, and set records as both the largest and the most expensive stunt ever filmed. The remaining two-thirds of the ship was added into the film during post-production by Industrial Light & Magic using computer-generated imagery (CGI).
