Bonfires and beacons showed the way for early tentative transcontinental flights in the 1920s. Now complex computerized systems of navigation and air traffic control manage skies filled with as many as 50,000 planes a day over the United States. Thanks to the airplane, much about the world has changed forever, not only its commerce and wars but also its dimensions. Now that it takes only a few hours to cross a continent or an ocean, the globe has grown small indeed. And propelling virtually every one of aviation's great leaps—from the first flight to the fastest jet—has been the solving of complex engineering problems.

The first of aviation's hurdles—getting an airplane off the ground with a human controlling it in a sustained flight—presented a number of distinct engineering problems: structural, aerodynamic, control, and propulsion. As the 19th century came to a close, researchers on both sides of the Atlantic were tinkering their way to solutions. But it was a fraternal pair of bicycle builders from Ohio who achieved the final breakthrough.

Orville and Wilbur Wright learned much from the early pioneers, including Paris-born Chicago engineer Octave Chanute. In 1894, Chanute had compiled existing information on aerodynamic experiments and suggested the next steps. The brothers also benefited from the work during the 1890s of Otto Lilienthal, a German inventor who had designed and flown several different glider models. Lilienthal, and some others, had crafted wings that were curved, or cambered, on top and flat underneath, a shape that created lift by decreasing the air pressure over the top of the wing and increasing the air pressure on the bottom of the wing. By experimenting with models in a wind tunnel, the Wrights gathered more accurate data on cambered wings than the figures they inherited from Lilienthal, and then studied such factors as wing aspect ratios and wingtip shapes.