Flight vehicles experience aeroelastic problems due to the interaction between structures and areodynamic forces. Aeroelastic instability is usually a critical porblem in transonic and lower supersonic regions. In present study, the aeroelastic analyses of several flight vehicles have been performed using the coupled techniques of computational fluid dynamics (CFD) and computational structural dynamics (CSD). Aerodynamic nonlinearities in transonic region are treated using the aeroelastic analysis system which include Navier-Stokes, Euler, and transonic small-disturbance (TSD) equations. THe aeroelastic characteristics of several aircraft models are investigated using the developed aeroelastic analysis system. On the other hand, structural nonlinearities always exist in flight vehicles. In the structural point of View, structural nonlinearity is classfied into distributed and concentrated one. Structural nonlinearities such as freeplay and large deformation effects are considered in the present aeroelasiec analysis system. Finally, asroelastic characteristics of several flight vehicles will be explained considering both aerodynamic and structural nonlinearities.