Abstract: An analytical method of gust alleviation and other active control purposes （relaxed static stability etc. ） for an airplane is described, Gust alleviation uses direct measurements of atmospheric turbulence to yield a feed-forward or open-loop control law. It is relatively insensitive to changes in flight conditions. Thus a combined control law can be obtained which contains feed-back and feed-forward components.The stability of the gust alleviation system and the performances of other active control purpose can be satisfied by obtaining a linear optimal control defined by a quadratic performance, index. Thus the performance index is combined, and the optimal feed-back control law is straightforward and well-known.An application of the combined control law to a flexible airplane is presented. Calculations have been performed to obtain the normal acceleration responses of the airplane to the turbulence and the state responses for the other active control purpose.