 The wing was considerably modified to improve low altitude performance, the span was reduced by 2 ft with the adoption of square-cut wingtips, the wing skins thickened, and the undercarriage modified to withstand the increased weight.3,268 Vampires were built in 15 versions, including twin-seat night fighters, trainers and carrier-based aircraft designated "Sea Vampire".The Vampire was used by 31 air forces.