The aim of this reprint is to present the current state of knowledge in the broad unmanned aerial vehicles (UAVs) discipline. With the rapid development of new applications and simulation methods, UAVs can now operate in a wide range of environmental conditions, thus extending the range of human activities due to their flexibility, autonomous control, size, low cost, and high adaptability. For this reason, the widely carried out multidisciplinary UAV research is of great importance in many fields. The intention of this collection was to bring together the work of leading researchers in the field of UAVs with an interest in their control, design, navigation, and autonomy. The papers included in this reprint present the key challenges of UAVs. The authors propose new solutions, approaches, and methodologies to address today's UAV challenges.