Description: A system for autonomous detection and exploitation of weather phenomena for endurance or range enhancement for loitering unmanned air vehicles is presented. The proposed system consists of hardware and software for coarse identification of geographical areas where advantageous weather phenomena (such as soaring conditions) are present. A custom autopilot and sensors enable the fine detection of the phenomena, and cause the UAV to adopt an optimal flight path that exploits the phenomena. The proposed system consists of custom hardware, software, and sensors. We have demonstrated a simulation of the system in Phase I, and we will render this in hardware in Phase II. We will also complete full flight test of the system on our 40 lb class UAV in Phase II.