What a wing actually does
A wing is a shaped surface that deflects air downward as it moves forward. By Newton’s laws, pushing air down pushes the wing up. The wing’s curved top and sloping underside also change the pressure distribution around it, with lower average pressure above and higher below. Popular explanations sometimes argue about whether the “faster air over the top” or the “turning of the airflow” is the true cause of lift, but both describe the same event from different angles, and they are linked in the mathematics of fluid flow. A simple way to remember the main controls is that lift grows with wing area, with speed (rapidly, as speed is squared) and with the angle at which the wing meets the air, up to a point at which the flow breaks away and the wing stalls.
Cayley and the idea of fixed wings
Early flight dreams focused on flapping. The English baronet George Cayley, working around the turn of the 19th century, separated the problem into parts: lift from fixed wings, thrust from a separate engine, control from tail surfaces. His 1799 engraving of a fixed-wing design is often considered a landmark. He built gliders, and an 1853 glider is traditionally reported to have carried a person, though details are disputed. His main contribution was a clear way of thinking about the problem.
Curved surfaces and Lilienthal
Many people assumed that flat boards would make good wings. Otto Lilienthal in Germany tested arched, or cambered, wing shapes and published his findings in the 1889 book on bird flight. Between 1891 and 1896 he made thousands of glider flights, hung beneath his wings and steering by shifting his weight. Data from this work, though imperfect, became a base for later experimenters. The Wright brothers began with Lilienthal’s tables, found them unreliable in some respects, and replaced them with their own wind tunnel measurements, which led to better wing shapes.
Warping and ailerons
The Wrights controlled roll by twisting the wingtips with cables, called wing warping. The idea worked, but the structure had to be flexible, and the technique was less suitable for stronger, faster aircraft. Hinged control surfaces on the trailing edge of the wing, called ailerons, did the same job by changing the lift on each side without twisting the wing. Early aileron ideas appeared in several places, and the exact credit is complicated and was the subject of patent disputes. By the First World War, ailerons were standard.
The biplane era
Most early aircraft used two wings, one above the other, braced with struts and wires. This was a sensible solution at the time: two thin wings joined by a truss could be strong and light, and engines were not powerful enough to need anything faster. A biplane provides a lot of wing area on a short span, helping low-speed lift. The drawbacks were drag from the struts and wires, and interference between the wings. As engines became more powerful, the penalty grew.
Monoplanes and strong materials
Single-wing aircraft existed early too. The Blériot XI monoplane, flown by Louis Blériot across the English Channel in July 1909, was a famous example. Yet monoplanes only became the norm when materials and structures allowed a wing strong enough to support itself without external bracing, known as a cantilever wing. The all-metal Junkers J 1 of 1915 was an early cantilever monoplane, and metal construction became more common through the 1920s and 1930s. Stressed-skin aluminum wings, retractable landing gear and flaps, which increase lift for landing and takeoff, helped make monoplanes the standard form for airliners and fighters by the Second World War. Wing flaps and slats also changed how pilots could land at lower speeds.
Swept wings and high speed
As aircraft approached the speed of sound, shock waves and a rise in drag became serious problems. German researchers in the 1930s and 1940s studied sweeping the wings back, which delays these effects, and the idea was widely developed after the war. Swept wings are a typical feature of jet airliners. Delta wings, shaped like triangles, also appeared on supersonic aircraft, including Concorde. Later research led to the supercritical airfoil, developed by NASA’s Richard Whitcomb, which has a flatter upper surface and reduces drag at high subsonic speeds.
Modern wings often include extra features like winglets, which reduce drag by weakening the vortices at the tips, and composite materials that save weight. Computer modeling now allows engineers to refine shapes in ways Cayley or the Wrights could not have attempted.
A continuing compromise
There is no perfect wing. A long, thin wing is efficient for gliding but may be hard to build strongly. A short, swept wing is good for speed but less so for slow flight. Every aircraft design is a compromise between purposes, which is why gliders, crop-dusters and airliners look so different.