The ‘Phantom Eye’ project is Boeing’s attempt to produce a HALE (High Altitude Long Endurance) aircraft. It is designed to use hydrogen for fuel, to fly at altitudes up to 65,000 feet, and stay aloft for four days while carrying a 450 lb payload.
Wikipedia says this:
The Phantom Eye demonstrator has a 150-foot (46 meter) wingspan. Boeing states that it can fly for more than four days at a time at altitudes of up to 65,000 feet. Boeing also states that the Phantom Eye demonstrator will be able to carry a 450 pound payload and have a cruising speed of 150 knots. The Phantom Eye carries no armament and is for “persistent intelligence and surveillance”.
Boeing says that they are using this aircraft as a test platform and that they want to build an even larger one that can stay up for ten days.
Another video of the second flight below.