Safety is the paramount objective of civil aviation. How safe is safe, is a question that pertains all the human activities, the integration of the remotely-piloted aircraft systems into the civil aviation system is based on the principle that existing safety will not be compromised. The book discusses briefly the risks inherent to the remotely-piloted aircraft operations, discusses the concept of risk, analyses the safety implications of the operations, and, addressing, in particular, the small remotely-piloted aircraft, provides some indications on how to conduct a safety risk assessment to verify the suitability of remotely-piloted aircraft systems to the operations.