starboard (right) wings. Occasionally, even more, wings have been used, with the three-winged triplane achieving some fame in World War I. The four-winged quadruplane and other multiplane designs have had little success. A monoplane, which derives from the prefix, mono means one which means it has a single wing plane, a biplane has two stacked one above the other, a tandem wing has two placed one behind the other. When the available engine power increased during the 1920s and 1930s and bracing was no longer needed, the unbraced or cantilever monoplane became the most common form of powered type. The wing planform is the shape when seen from above. To be aerodynamically efficient, a wing should be straight with a long span from side to side but have a short chord (high aspect ratio). But to be structurally efficient, and hence lightweight, a wing must have a short span but still enough area to provide lift (low aspect ratio). At transonic speeds, near the speed of sound, it helps to sweep the wing backward or forwards to reduce drag from supersonic shock waves as they begin to form. The swept wing is just a straight wing swept backward or forwards. The delta wing is a triangle shape which may be used for a number of reasons. As a flexible Rogallo wing it allows a stable shape under aerodynamic forces, and so is often used for kites and other ultralight craft. As a supersonic wing, it combines high strength with low drag and so is often used for fast jets. A variable geometry wing can be changed in flight to a different shape. The variable-sweep wing transforms between an efficient straight configuration for takeoff and landing, to a low-drag swept configuration for high-speed flight. Other forms of variable planform have been flown, but none have gone beyond the research stage. Fuselage A fuselage is a long, thin body, usually with tapered or rounded ends to make its shape aerodynamically smooth. Most fixed-wing aircraft have a single fuselage, often referred to as simply "the body". Others may have two or more fuselages, or the fuselage may be fitted with booms on either side of the tail to allow the extreme rear of the fuselage to be utilized. The fuselage may contain a flight crew, passengers, cargo or payload, fuel and engine(s). Pilotless aircraft (drones) do not usually have a pilot or any