A brief review of sliding model control is undertaken, with particular emphasis upon the effects of neglected parasitic dynamics. Sliding model control design is interpreted in the frequency domain. The inclusion of asymptotic observers and control 'hedging' is shown to reduce the effects of neglected parasitic dynamics. An investigation into the application of observer-based sliding mode control to the robust longitudinal control of a highly unstable is described. The sliding mode controller is shown to exhibit stability and performance robustness superior to that of a classical loop-shaped design when significant changes in vehicle and actuator dynamics are employed to model airframe damage.Vetter, T. K. and Wells, S. R. and Hess, Ronald A. and Bacon, Barton (Technical Monitor) and Davidson, John (Technical Monitor)Langley Research CenterFLIGHT CONTROL; DAMAGE; AIRCRAFT; FAILURE; AIRFRAMES