A procedure for incorporating a key non-linear aerodynamic characteristic into the design optimization of a high-speed civil transport has been developed. Previously, the tendency of a high-speed aircraft to become uncontrollable (pitch-up) at high angles-of-attack during landing or takeoff for some wing shapes could not be included directly in the design process. Using response surface methodology, polynomial approximations to the results obtained from a computationally expensive estimation method were developed by analyzing a set of statistically selected wing shapes. These response surface models were then used during the optimization process to approximate the effects of wing planform changes on pitch-up. In addition, response surface approximations were used to model the effect of horizontal tail size and wing flaps on the performance of the aircraft. Optimizations of the high-speed civil transport were completed with and without the response surfaces. The results of this study provide insight into the influence of nonlinear and more detailed aerodynamics on the design of a high-speed civil transport. / Master of Science