This paper focusses on differential thrust quadcopters, whose flight envelope can be divided in two, namely: the quadrotor flight envelope, and the airplane flight envelope. We define a transition maneuver as a controlled path followed by an aircraft in order to move between the two flight envelopes. We propose a control law that is robust with respect to wind disturbances and unmodeled aerodynamic effects. This approach ensures that the aircraft does not fall down during the transition maneuver.