Dynamic aeroelasticty is considered and the dynamic stability (Flutter) of linear aeroelastic systems is considered as well as the response to external disturbances including atmospheric turbulence (Gusts). The discussion proceeds from simpler physical models and mathematical methods to more complex ones. An introduction to the modeling of aerodynamics forces is also provided to prepare the reader for the material in chapter ‘Nonsteady Aerodynamics of Lifting and Non-lifting Surfaces’.