A compound aircraft having a fuselage, a main rotor, a main anti-torque device and two wings positioned on either side of the fuselage. Each wing has at least one movable flap situated at its trailing edge. The flaps can be deflected asymmetrically relative to an air stream generated in reaction to the lift of the main rotor on either side of the fuselage so as to create longitudinal aerodynamic forces in opposite directions on either side of the fuselage and consequently create an additional torque that is added to the main torque from the main anti-torque device.