On May 30, 1899, Wilbur Wright of Dayton, OH wrote to the Smithsonian Institution in Washington, D.C. saying, "My observations have convinced me more firmly that human flight is possible and practicable. I wish to obtain such papers as the Smithsonian Institution has published on this subject, and if possible a list of other works in print in the English language."
In this letter, Wilbur had made mention of his interest in birds. To achieve human flight, he had written, was "only a question of knowledge and skill in all acrobatic feats," and birds were "the most perfectly trained gymnasts in the world...specially well fitted for their work." On Sundays, he would ride off on his bicycle to spend considerable time there observing birds.
For Wilbur and Orville, the dream had taken hold. They would design and build their own experimental glider-kite, drawing on much they had read, much they had observed about birds in flight, and importantly, from considerable time thinking.
Equilibrium was the all-important factor, the brothers understood. The difficulty was not to get into the air but to stay there. Wilbur's observations of birds in flight had convinced him that birds used more "positive and energetic methods of regaining equilibrium" than that of a pilot trying to shift the center of gravity with his own body. It had occurred to him that a bird adjusted the tips of its wings so as to present the tip of one wing at a raised angle, the other at a lowered angle. Thus its balance was controlled by "utilizing dynamic reactions of the air instead of shifting weight."
On an evening at home, using a small cardboard box from which he had removed the ends, Wilbur put on a demonstration before Orville and his sister Katharine. He showed them how, by pressing the opposite corners of the box, top and bottom, the double wings of a biplane glider could be twisted or "warped," to present the wing surfaces to the air at different angles or elevations, the same as the birds did. Were one wing to meet the wind at a greater angle than the other, it would give greater lift on that side and so the glider would bank and turn.
With "wing warping," or "wing twisting," as it was sometimes referred to, Wilbur had already made an immensely important and altogether original advance toward their goal.
In the summer of 1899, in a room above their bicycle shop, the brothers began building their first aircraft, a flying kite made of split bamboo and paper with a wingspan of five feet. It was a biplane, with double wings, one over the other, the design to provide greater stability.
In 1901, they flew their glider as a kite and after that they designed and successfully tested their Kitty Hawk Aeroplane on December 17, 1903 at Kitty Hawk, North Carolina.