The engineering field of aeroservoelasticity in flexible flight vehicles involves mathematical modeling, analysis, and control of the interaction between aerodynamics, structural, and flight dynamic systems along with wind tunnel and flight testing of the advanced active control technology. Adverse aerodynamic‐structure‐control interactions of flexible aircrafts have been a major problem throughout the history of aeronautics. If the flexible vehicle structure is not properly designed, aerodynamic‐structure interactions at high speeds may cause excessive dynamic responses leading to an instability or catastrophic structural failure. In this chapter, fundamentals of these aerodynamic‐structure interactions and optimal feedback control of the resulting flight dynamic instabilities are presented. First, a brief historical review of the evolution of aeroservoelasticity and active control of aeroelastic responses is presented. Then, basic mathematical formulation and analytical modeling techniques for a general aeroservoelastic system along with fundamentals of optimal robust feedback control law design processes are outlined. Techniques for large flexible aircraft structural deformation modal control, bending torsion flutter suppression, and gust load alleviation systems are explained. Two examples of research projects are presented that have demonstrated flutter suppression and gust load alleviation of aeroservoelastic models in wind tunnel tests. Finally, possible future directions of this exciting field of applied aerospace engineering technology and their applications to advanced aircrafts are discussed.