In this work is treated the design of two controllers applied to a fixed-wing unmanned aerial vehicle (UAV). The aim is to stabilize an UAV type Cessna 182 in longitudinal and in lateral-directional flight. The UAV is identified by decoupling the system to longitudinal and lateral-directional modes and using off line modeling. The resulting models represent approximately the UAV because of nonlinearities and parametric uncertainties characterizing it. This lack of accuracy makes the UAV difficult to control. Hence the necessity to implement a robust laws control. In this work, the controllers are based on Terminal Sliding Mode (TSM) and cascade control PID-TSMC. A comparative study between the two control laws is performed in order to determine the controller that offers best performance. Simulation results are used to analyze the two controllers. They demonstrate the robustness of TSMC towards parametric uncertainties and external disturbances. This command is improved in terms of accuracy by adding a PID as an outer loop.