The history of flight

The first people to fly rode in a hot-air balloon built by the Montgolfier brothers, which carried two passengers over Paris in November 1783. Heated air is less dense than the cooler air around it, so the balloon rises, the same principle that lifts a cork in water.

Balloons could rise but not steer. In the nineteenth and early twentieth centuries, airships added engines and rudders, and German Zeppelins carried passengers across the Atlantic. The hydrogen-filled Hindenburg's fiery destruction in 1937 effectively ended the passenger airship era.

An aircraft wing is shaped and angled so that it deflects air downward as it moves forward. By Newton's third law, pushing air down pushes the wing up. The same flow produces lower pressure above the wing than below it. Both descriptions are two views of the same physics, and together they explain lift.

Four forces act on an aircraft in flight: lift upward, weight downward, thrust forward and drag backward. To climb, lift must exceed weight; to speed up, thrust must exceed drag.

The English engineer George Cayley identified these forces around 1800 and built gliders. In Germany, Otto Lilienthal made around 2,000 glider flights in the 1890s and published detailed data, before dying after a crash in 1896.

Orville and Wilbur Wright, bicycle makers from Ohio, studied the problem systematically. They built a wind tunnel to test wing shapes and, crucially, worked out how to control a plane in three dimensions, using wing-warping to roll. On 17 December 1903 at Kitty Hawk, North Carolina, their Wright Flyer made the first controlled, sustained, powered flight by a heavier-than-air machine. The first flight lasted 12 seconds and covered 36 metres.

Aviation advanced rapidly during the First World War, when aircraft moved from reconnaissance to fighting and bombing. In 1927 Charles Lindbergh flew solo nonstop from New York to Paris, and the 1930s brought all-metal passenger airliners such as the Douglas DC-3.

Frank Whittle in Britain and Hans von Ohain in Germany independently developed the jet engine, which sucks in air, compresses it, burns fuel in it and blasts the hot gas out the back. The first jet aircraft flew in 1939. In 1947 Chuck Yeager flew faster than the speed of sound in the rocket-powered Bell X-1.

• The de Havilland Comet began the first jet airliner service in 1952.
• The Boeing 707, entering service in 1958, made jet travel commercially successful.
• The Boeing 747 jumbo jet, from 1970, dramatically lowered the cost per seat.
• Concorde carried passengers at twice the speed of sound from 1976 until 2003.
• Deregulation and low-cost airlines from the late twentieth century turned flying into routine travel for millions.

Commercial aviation is now one of the safest forms of transport per distance travelled. That record comes from careful investigation of every accident, strict maintenance, redundant systems, standard procedures and a culture of reporting mistakes.

Aviation's biggest challenge is climate. Aircraft burn kerosene, and flying is hard to decarbonise because batteries are too heavy for long flights. Options under development include sustainable aviation fuels, more efficient aircraft designs, hydrogen propulsion and electric aircraft for short routes.