An aircraft comprising a device for influencing the directional stability of the aircraft, with the aircraft comprising: wings (10a, 10b) with ailerons (11a, 11b) and a rudder, with the device for influencing the directional stability of the aircraft comprising: - a sensor device that is functionally connected with the flight control device, for acquiring the rotation rates, including the yaw rates, of the aircraft, - in each case at least one actuator, which is functionally connected with the flight control device, for adjusting the ailerons (11a, 11b) and for adjusting the rudder, - a flight control device that is functionally connected with a control-input device, wherein the flight control device comprises a control function that is designed in such a manner that from the control demands and the rotation rates said flight control device generates adjusting commands for the actuators for controlling the aircraft and transmits them to said actuators, characterised by: - two tail-mounted flaps (K1, K2), situated behind the connecting region of the wings (10a, 10b) and on opposite sides of the fuselage, each tail-mounted flap (K1, K2) being coupled to an actuator (61, 62) that is functionally connected with the flight control device for moving the tail-mounted flaps (K1, K2) between a retracted and an extended position, wherein the tail-mounted flaps (K1, K2) are designed such that in their retracted state the exterior surfaces of the same form streamlined parts of the exterior surface of the fuselage and that in their extended position the respective tail-mounted flap (K1, K2) projects outwards from the exterior skin of the fuselage into the air that flows around the fuselage, in order to influence the flow at this position, - and in that the control function is designed in such a manner that for lateral control of the aircraft, on the basis of rotation rates about the Z-axis of the aircraft acquired by the sensor device, the control function generates commands for actuating of at least one of the tail-mounted flaps (K1, K2) and transmits the commands to said actuator (61, 62) for actuating the tail-mounted flaps (K1, K2) such that a moment about the vertical Z-axis of the aircraft is effected. - a sensor device that is functionally connected with the flight control device, for acquiring the rotation rates, including the yaw rates, of the aircraft, - in each case at least one actuator, which is functionally connected with the flight control device, for adjusting the ailerons (11a, 11b) and for adjusting the rudder, - a flight control device that is functionally connected with a control-input device, wherein the flight control device comprises a control function that is designed in such a manner that from the control demands and the rotation rates said flight control device generates adjusting commands for the actuators for controlling the aircraft and transmits them to said actuators, characterised by: - two tail-mounted flaps (K1, K2), situated behind the connecting region of the wings (10a, 10b) and on opposite sides of the fuselage, each tail-mounted flap (K1, K2) being coupled to an actuator (61, 62) that is functionally connected with the flight control device for moving the tail-mounted flaps (K1, K2) between a retracted and an extended position, wherein the tail-mounted flaps (K1, K2) are designed such that in their retracted state the exterior surfaces of the same form streamlined parts of the exterior surface of the fuselage and that in their extended position the respective tail-mounted flap (K1, K2) projects outwards from the exterior skin of the fuselage into the air that flows around the fuselage, in order to influence the flow at this position, - and in that the control function is designed in such a manner that for lateral control of the aircraft, on the basis of rotation rates about the Z-axis of the aircraft acquired by the sensor device, the control function generates commands for actuating of at least one of the tail-mounted flaps (K1, K2) and transmits the commands to said actuator (61, 62) for actuating the tail-mounted flaps (K1, K2) such that a moment about the vertical Z-axis of the aircraft is effected.