This paper discusses energy extraction from atmospheric turbulence by small- and micro- uninhabited aerial vehicles. A nonlinear longitudinal dynamic model of a glider with elevators as the sole control input is used for the aircraft and feedback control laws for energy extraction are discussed. Using current measurements of wind speed and gradient the state which maximizes the gain in total energy is computed. A state feedback controller uses elevator input to regulate states to the optimal values. The state feedback control law is computed using LQR synthesis, and the state and input weight matrices which maximize energy gain are found using a search method. Simulation results of flights through sinusoidal gust fields and a thermal field show the performance of the proposed approach.