The aim of this book is to design a High Altitude and Long Endurance (HALE) UAV after comparing and analyse the existing solar powered UAVs that has to be used in variety of applications as for military as well as commercial purposes. The aircraft design developed is a light and low drag flying wing configuration with solar cells as major power source.The Book includes the conceptual and detail design of the aircraft with stability, propulsion, performance, structural and fluid analysis, and also the fabrication of a prototype flying model for the demonstration and verification of the concept.