Nowadays, mini Unmanned Aerial Vehicles (UAVs) are utilized in a wide range of reconnaissance and surveillance missions with an ever increasing need for endurance and range. Thus, a slight improvement on these two primary performance parameters is considered as a competitive advantage. In this work, a multi-functional tailless UAV concept and its design process is presented. In comparison to existing conventional UAV designs, the concept is shown to have superior aerodynamic and flight performance characteristics. In addition the detachable wing and body concept provides the much needed flexibility and multi-functionality for using the UAV for a range of operation concepts, in which each concept requires different payloads of distinct weight and size.