Phantom Eye is a liquid hydrogen-fueled, high-altitude and long-endurance unmanned aircraft system for persistent intelligence, surveillance and reconnaissance and communications missions. The demonstrator aircraft is capable of maintaining its altitude for up to four days while carrying a 450-pound payload. Typical payloads include multiple sensor packages for monitoring, tracking and communications. A full size Phantom Eye variant is designed to stay aloft for up to ten days and carry a payload of 2,000 pounds.