The development of closed loop control has been one of the major technological achievements of the twentieth century, and its concepts married with analogue and digital computation led to explosive growth in the sophistication of the technology and the ubiquity of its application. By that, an automatic flight control system is able to stabilize an inherently unstable airplane or to provide a stability augmentation system (SAS). In other words, there is no margin for error in its response to atmospheric disturbances and to commands that come from navigation system. Moreover it improves the handling qualities, the flight comfort and reduces the costs when an airplane is under control of an autopilot. This specific project is destined to simulate and analyze the operating parameters (i.e., altitude, pitch angle, airspeed, throttle level, and elevator angle) of a passenger aircraft - Boeing 747-100 –in longitudinal motion deflected from its ordered flight trajectory and atmospheric condition when related with its reference steady flight parameters. For all cases studied, the results are satisfactory controlled and expected. Future works can be done in using the differential equations instead of linearized ones, which increases the range of possible cases to be studied.