A glider is a heavier-than-air aircraft that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free flight does not depend on an engine. The first heavier-than-air machine to achieve free flight was built by George Cayley and flown in 1853. Since then, gliders have been designed and built for a wide variety of flying tasks including recreation, racing, military operations, and other specialized roles.
Gliders are aerodynamically streamlined and are capable of very efficient unpowered flight. The best glide ratio (the ratio of forward travel to descent) achieved in level flight by a typical glider is about 15:1; this means that for every 15 meters (50 ft) of forward travel, the glider will descend 1 meter (3 ft). The largest wing span ever achieved on a glider is 79.4 meters (260 ft), on the Eipper Formance Gull 2000 which was designed to fly from Australia to New Zealand nonstop. However, such wingspan/glide ratio records are only meaningful when all other design parameters are also optimized; in particular a low aspect ratio wing will usually have better glide performance than one with high aspect ratio at any given wing span.