Almost as soon as the turbojet emerged in the 1940s, engineers began looking for ways to hush the engine and increase its efficiency. The solution, which first appeared in engines on the Douglas DC-8, was a large fan, driven by the turbine, that heaved masses of cold air rearward, bypassing the combustion chamber and mixing with its hot exhaust.
Airplanes with ’em can fly farther than airplanes without ’em. They have the effect of increasing the wing’s span, and therefore its lift, without increasing its length. The first airliner to use them was the 747-400 in 1988, and you’ll see them on almost all Boeing airliners (Airbus uses wing fences for the same benefits).
For seven other inventions that have made air travel what it is today, see the photo gallery at right. - the editors.