In this project, the effect of aircraft body flexibility in aerodynamic mode was studied. In the second section, assuming creation of bending in the body by horizontal and vertical tails, the longitudinal and transverse stability derivatives of the aircraft were obtained and, as shown, body flexibility reduced stability of the aircraft and also reduced power of tail control surfaces. This decrease increases with increasing speed such that these effects are noticeable at higher speeds. In the next section, natural frequencies of aircraft structure were obtained by discretization of continuous masses into discrete concentrated masses, and as observed, as the number of masses increased, the obtained results became more accurate and converged toward real value. However, if the plane is subjected to unplanned maneuver of plunging in critical conditions and given the fact that the aircraft has not been designed for such maneuvers, the impact of body flexibi-lity in such conditions would be significant, that as was observed, through aerodynamic considerations and ABAQUS software outputs, airplanes can achieve complete safety. After aerodynamic examination of flight of elastic airplanes, the issue of controlling these planes can be considered. For this purpose, it is necessary to obtain airplane conversion function with regard to flexibility of the structure. In this case, the zeros and poles of elastic airplane conversion function will be different from stiff state and require specific measures.