Design of an effective autopilot control system for Lighter-Than-Air (LTAs) vehicles, especially for stratospheric airship is crucial. A Stratospheric Airship Platform (SAP) is required to perform various autopilot control actions to satisfy the mission requirements. The main control actions are holding altitude, velocity, pitch and bank angles at desired operating conditions, which are also important for autonomous navigation and guidance purposes. Proportional-Integral-Derivative (PID) is one of the traditional control algorithms and plays key role in the achievement of given requirements. In this paper, a successive loop closure design method has been implemented and compared with respect to the autopilot control actions mentioned above. Successive loop of PI controller is used to emphasize more on steady state behavior rather than transient behavior of the autopilots. Graphical User Interface (GUI) is developed in SISO architecture tool in MATLAB® for the simulation of different autopilots. Simulation results show that designed autopilots are optimal in terms of transient and steady state specifications. © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.