A brief starting point
On December 17, 1903, near Kitty Hawk, North Carolina, Orville and Wilbur Wright made four short flights in a powered, controllable aircraft. The longest lasted under a minute. Everything in this article builds on that start, but its subject is a narrower question: how did flight go from a noisy propeller machine carrying one or two people to a jet airliner carrying hundreds? The answer runs through engines, and through a long period when many experts doubted that jets could ever be practical for passengers.
The propeller era and its limits
For about four decades, aircraft used piston engines turning propellers. The engines grew far more powerful and reliable, and by the 1930s airliners such as the Douglas DC-3 made scheduled air travel normal for many people. After the Second World War, large piston-engined airliners, including the Douglas DC-6 and the Lockheed Constellation, flew longer routes with pressurized cabins that allowed cruising at higher altitudes.
Even so, the piston engine had limits. Adding power meant adding cylinders, weight, complexity and vibration, and propellers become inefficient as their blade tips approach the speed of sound. Designers of aircraft engines and airplane propellers had squeezed out a great deal, but the next big gain needed a different kind of engine.
Two inventors of the jet engine
The gas turbine jet engine was developed independently in two countries. Frank Whittle, a British Royal Air Force officer, patented a turbojet design in 1930, and a test engine first ran in 1937. In Germany, Hans von Ohain worked with the Heinkel company and a jet-powered Heinkel He 178 flew on August 27, 1939, generally regarded as the first flight of a jet-propelled aircraft. Britain’s Gloster E.28/39 followed in 1941.
Jet fighters entered service late in the Second World War, including the German Messerschmitt Me 262 and the British Gloster Meteor. They were fast but thirsty, and engine life was short. After the war, engineers worked to improve fuel use and reliability, and military jets such as the Bell X-1 rocket plane, which exceeded the speed of sound in 1947, showed what faster flight might demand from aircraft structure.
Early passenger jets
The de Havilland Comet, a British airliner, began passenger service in 1952 and is commonly described as the first jet airliner in regular service. It was fast and smooth compared with piston aircraft, and passengers noticed the difference. In 1954, though, two Comets broke up in flight. Investigators eventually concluded that metal fatigue, with cracks starting near the corners of the square windows, had weakened the pressurized fuselage. The Comet was redesigned, and lessons from the inquiry changed how engineers test and design pressurized airframes.
Another development was the turboprop, which uses a jet-type turbine to drive a propeller. The Vickers Viscount, which entered service around 1950, was among the first and was popular on shorter routes.
The Boeing 707 began transatlantic service with Pan American in October 1958, and the Douglas DC-8 followed shortly after. Sweptback wing design and engines slung beneath the wings in pods became the standard layout. Within a few years, jets were carrying most long-distance passengers, and trips that had taken a day or more across the Atlantic took hours.
Bigger and quieter engines
Early jets used turbojets, which are loud and use a lot of fuel at low speeds. The turbofan, in which a large fan moves extra air around the engine core, improved both. High-bypass turbofans, developed in the 1960s, powered the Boeing 747, which entered service in 1970 and was for many years the largest passenger aircraft. Its capacity helped lower the cost per seat on long routes, and airline travel became more affordable to a wider group of people over the following decades.
Supersonic passenger flight was tried too. Concorde, built by British and French manufacturers, flew passengers from 1976 until 2003. It was technically impressive but costly to run and noisy, and it never led to a lasting class of supersonic airliners.
Modern airliners
Today’s jet airliners owe much to refinements rather than to dramatic breakthroughs. Engines are more efficient and quieter than those of the 707 era. Fly-by-wire controls, introduced in airliners in the late 1980s, use computers to link the pilot’s inputs to the control surfaces. Composite materials appear more widely in structures, and newer models have been designed with fuel economy as a central goal. At the same airports, air traffic control systems and radar-based tracking help manage large numbers of flights safely, which is as important to modern air travel as the aircraft themselves.
The jump from 1903 to the jet age took roughly half a century of work by many people and companies. The Wright brothers showed that controlled powered flight was possible; the jet engine made it fast enough, and later design work made it routine.