During their experiments of 1902 the Wrights succeeded in controlling their glider in all three axes of flight: pitch, roll and yaw. Their breakthrough discovery was the simultaneous use of roll control (with wing-warping) and yaw control (with a rear rudder). A forward elevator controlled pitch. In March 1903 they applied for a patent on their method of control. The application, which they wrote themselves, was rejected. In early 1904, they hired Ohio patent attorney Henry Toulmin, and on May 22, 1906, they were granted U.S. Patent 821393 for a "Flying Machine".
The patent's importance lies in its claim of a new and useful method of controlling a flying machine, powered or not. The technique of wing-warping is described, but the patent explicitly states that other methods instead of wing-warping could be used for adjusting the outer portions of a machine's wings to different angles on the right and left sides to achieve lateral (roll) control.
The concept of lateral control was so basic to any aircraft design that, without it, no aircraft could have flown successfully.
The broad protection intended by this patent succeeded when the Wrights won patent infringement lawsuits against Glenn Curtiss and other early aviators who devised ailerons to emulate lateral control described in the patent and demonstrated by the Wrights in their 1908 public flights. U.S. courts decided that ailerons were also covered by the patent.