Rather than controlling the craft by altering the center of gravity by shifting the pilot's body weight as Lilienthal had done, the Wrights intended to balance their glider aerodynamically. They reasoned that if a wing generates lift when presented to an oncoming flow of air, producing differing amounts of lift on either end of the wing would cause one side to rise more than the other, which in turn would bank the entire aircraft. A mechanical means of inducing this differential lift would provide the pilot with effective lateral control of the airplane. The Wrights accomplished this by twisting, or warping, the tips of the wings in opposite directions via a series of lines attached to the outer edges of the wings that were manipulated by the pilot. The idea advanced aeronautical experimentation significantly because it provided an effective method of controlling an airplane in three-dimensional space and, because it was aerodynamically based, it did not limit the size of the aircraft as shifting body weight obviously did. The satisfactory performance of the 1899 kite demonstrated the practicality of the wing warping control system.
Encouraged by the success of their small wing warping kite, the brothers built and flew two full-size piloted gliders in 1900 and 1901. Beyond the issue of control, the Wrights had to grapple with developing an efficient airfoil shape and solving fundamental problems of structural design. Like the kite, these gliders were biplanes. For control of climb and descent, the gliders had forward-mounted horizontal stabilizers. Neither craft had a tail. The Wrights' home of Dayton, Ohio, did not offer suitable conditions for flying the gliders. An inquiry with the U.S. Weather Bureau identified Kitty Hawk, North Carolina, with its sandy, wide-open spaces and strong, steady winds as an optimal test site. In September 1900, the Wrights made their first trip to the little fishing hamlet that they would make world famous.
Although the control system worked well and the structural design of the craft was sound, the lift of the gliders was substantially less than the Wrights' earlier calculations had predicted. They began to question seriously the aerodynamic data that they had used. Now at a critical juncture, Wilbur and Orville decided to conduct an extensive series of tests of wing shapes. They built a small wind tunnel in the fall of 1901 to gather a body of accurate aerodynamic data with which to design their next glider. The heart of the Wright wind tunnel was the ingeniously designed pair of test instruments that were mounted inside. These measured coefficients of lift and drag on small model wing shapes, the terms in the equations for calculating lift and drag about which the brothers were in doubt.