High Altitude Long Endurance (HALE) aircraft have garnered increased interest in recent years as they can serve several purposes, including many of the objectives of satellites while incurring a fraction of the cost to deploy. Examples applications include Intelligence, Surveillance, and Reconnaissance, communications relay systems, and environmental and atmospheric sensing. The requirements for HALE aircraft dictate that they have very high lift-to-drag ratios, and are extremely lightweight, resulting in high aspect ratios with significant structural flexibility. This results in a dynamically nonlinear vehicle with highly coupled rigid body and aeroelastic structural dynamics. Atmospheric turbulence and gust loading of substantial variance can significantly impact the performance of HALE aircraft. Due to the vast importance of gust loading on these lightweight aircraft platforms, Systems Technology, Inc. and the University of Michigan propose the development of the Disturbance Observer for Gust Load Alleviation (DOGLA) where the gust loading will be actively estimated and subsequently rejected. DOGLA will be implemented on a nonlinear HALE aircraft model in conjunction with a robust primary flight control design. Both the disturbance observer and primary flight control designs will be implemented within a novel gain-scheduling framework to address nonlinear dynamics and varying flight conditions.