Unmanned Aircraft Systems (UAS) have seen unprecedented levels of growth during the last decade in both military and civilian domains. It is anticipated that civilian applications will be dominant in the future, although there are still barriers to be overcome and technical challenges to be met. Integrating UAS into, for example, civilian space, navigation, automy, see-detect-and-avoid systems, smart designs, system integration, vision-based navigation and training, to name but a few areas, will be of prime importance in the near future. This is an edited book composed of peer reviewed papers presented in the 2011 International Conference on UAS. The papers present the state of the art in UAS, as well as current developments and applications. This book aims at serving as a guide tool on UAS for engineers and practitioners, academics, government agencies and industry. This is a spin-off edition also published in the Journal of Intelligent and Robotic Systems (JINT), Volume 65: 1-4.