Motivation for the investigation of a 3D-trajectory control is the demand for Unattended Aerial Systems (UAS) capable of fulfilling e.g. surveillance tasks in contaminated or in inaccessible areas without any assistance of a human pilot. Hence, this paper deals with the development of such a control algorithm able to follow any kind of 3D-trajectory.In the following chapters the 3D-trajectory control algorithm is described. Many simulations were done to find the optimal trajectory course. Further, the control algorithm was implemented on a flight demonstrator for validation and experimental results are provided.