This paper addresses the stability and tracking control problem of an underactuated four rotor unmanned flying robot vehicle. Algorithm design combines adaptive law with the sliding mode control term to deal with uncertainties associated with flying environment, mass, inertia, aerodynamic force and moment of the vehicle. Using Lyapunov analysis, we show that the position and orientation tracking errors and their derivatives are bounded by bounds that can be made close to the origin. Simulation examples on a quadrotor vehicle are given to demonstrate the effectiveness of theoretical development for real-world application.