The aim of this study is to design a landing control system and test it on X-Plane flight simulator. Model-Following control and H-Infinity output feedback control methods are used to design the controller. In the flare part of the automatic landing system, it is desired to reduce the rate of descent in order to make aircraft touch down softly. This is accomplished by exponential decay trajectory. The trajectory which is drawn by the referenced model is followed by the linearized aircraft model. The error between commanded altitude and the current altitude converges to zero before touch down. Controller gains used in the model-following control design are calculated by using the H-Infinity output feedback control method since not all the state variables will be available for feedback in actual flight. Aircraft control commands for the flare control design in Matlab-Simulink environment are sent to the aircraft model in X-Plane flight simulator via User Datagram Protocol (UDP) and then the measured aircraft output variables are received simultaneously. The results provided in this study show that the aircraft in X-Plane flight simulator which has a nonlinear environment can be controlled by the model-following controller to satisfy the landing flare requirements. Robustness of the controller will also be evaluated against modeling errors and external disturbances.