To simulate flight conditions, the Wrights tested small model wings in a wind tunnel they had built. The wind tunnel was a box with a fan at one end that blew a steady stream of air over model wings mounted on a special "balance" inside the tunnel. Using this device, the brothers were able to gather information that could be used to design the wings of the gliders and powered aircraft that would carry them into the air. The wind tunnel provided them with information on the most satisfactory wing shape. It also enabled them to calculate the size of wing that would be required to lift them into the air, the performance of their propellers, and the amount of power that their engine would have to produce. They based the design of their next glider on this information.

During the 1901 glider tests, the Wright brothers had discovered that "wing warping" created unequal drag on the two wings. Key to solving the control problem was the addition of a rudder to the glider design in 1902. They developed a direct linkage between the rudder and warping system. With the success of this system design, the Wrights were ready to move onto a powered aircraft.

Orville and Wilbur took turns making three more flights that morning. Wilbur was at the controls for the fourth and longest flight, traveling 260 meters in 59 seconds. The Wright 1903 Flyer became the first powered, heavier-than-air machine to achieve controlled, sustained flight with a pilot aboard. Today, this amazing flying invention can be viewed as it is suspended overhead, at the National Air and Space Museum in Washington, D.C.