As the roles of UAVs in the aerospace arena increase, there is much interest in increasing their ability to operate autonomously without the need of operator intervention. The following paper describes the development and testing of an autonomous UAV system capable of completing complex surveillance missions. The system has to search for its target building in a predefined search area, find an entry point on the target building and finally enter the building to transmit images from within the building back to a ground control station, all without the interaction of a human operator. Such complex missions require development of algorithms from multiple disciplines such as image processing, target tracking and estimation, and GNC(Guidance, Navigation and Control) algorithms. Furthermore a sophisticated mission manager is required to synchronize the operation of the separate subsystems and that is capable of autonomously making operational decisions. This paper will present the development of these various algorithms and flight test results of the autonomous system.