On the morning of October 5, 1905, Amos Stauffer and a field hand were cutting corn when the distinctive clatter and pop of an engine and propellers drifted over from the neighboring pasture. The Wright boys, Stauffer knew, were at it again. Glancing up, he saw the flying machine rise above the heads of the dozen or so spectators gathered along the fence separating the two fields. The machine drifted toward the crowd, then sank back to earth in a gentle arc. The first flight of the day was over in less than 40 seconds.

By the time Stauffer and his helper had worked their way up to the fence line, the airplane was back in the air and had already completed four or five elliptical sweeps around the field, flying just above the level of the treetops to the north and west. “The durned thing was still going around,” Stauffer recalled later. “I thought it would never stop.” It finally landed 40 minutes after takeoff, having flown some 24 miles and circled the field 29 times.

Farmer Stauffer had been watching the goings-on in that Ohio cow pasture for two years, but he had never seen anything like this. Neither had anyone else. The 1905 Wright Flyer was the final link in an evolutionary chain of seven experimental aircraft: one kite (1899); three piloted gliders (1900, 1901, 1902); and three powered airplanes (1903, 1904, 1905). Each machine was a distillation of the lessons learned and the experience gained with its predecessors. The flight of October 5, 1905, was proof that the Wrights had achieved their goal of developing an aircraft that could be flown reliably over significant distances under the pilot’s complete control. Six years of trial and error, discouragement and hope, disappointment and exhilaration, risk to life and limb, and brilliant engineering effort had ended in triumph.

Over a century later, the basic question remains. Why Wilbur and Orville? When the brothers began their aeronautical research in the spring of 1899, they seemed unlikely candidates to achieve the age-old dream of navigating the air. They were not college-educated men. Wilbur, 31, and Orville, 28, were living in their father’s house while operating a neighborhood bicycle sales and repair shop, where they had just begun to build cycles, one at a time.

Yet these two apparently ordinary small businessmen were intuitive engineers, possessed of unusual talents, insights, and skills that perfectly suited them to the problem at hand. They had an instinctive grasp of the process of innovation—and a rare ability to imagine a machine that had yet to be built and to visualize how it would function. They could move from the abstract to the concrete with relative ease, as in the fall of 1901, when they designed a pair of wind-tunnel balances as mechanical analogues of the algebraic equations they had to apply to calculate the performance of the aircraft they were designing.

The passion that the brothers brought to solving difficult technical problems was another essential key to their