What may be the most important contribution of the flying qualities evaluation programs and experiments conducted on the variable stability aircraft at Ames was George Cooper's standardized system for rating an aircraft's flying qualities. Cooper developed his rating system over several years as a result of the need to quantify the pilot's judgment of an aircraft's handling in a fashion that could be used in the stability and control design process. This came about because of his perception of the value that such a system would have, and because of the encouragement of his colleagues in the United States and England who were familiar with his initial attempts.