Planform refers to the shape and layout of the fuselage and wing of a fixed wing aircraft. Aviation history presents an almost endless variety of planforms that have been utilised in experimental and production aircraft. In general terms, these designs can be grouped based on the intended speed of the aircraft concerned. The most common planform for low speed aircraft is the straight wing and its variants. Conversely, for high speed (transonic or supersonic) aircraft, the usual planforms are the swept wing and, less commonly, the delta wing.