DARPA's Autonomous High-Altitude Refueling (AHR) program hopes to bring autonomous refueling to the Global Hawk and other flying robots. A recent DARPA news release says the AHR program has completed a test flight that brings their goal one step closer. During the test, two Global Hawks flew within 100 feet or less of each other for 2.5 hours at 44,800 feet. The aircraft were fitted with a refueling probe and a receiver drogue, which were brought into the correct orientation to connect but were not actually connected during this test flight. According to Jim McCormick of DARPA:

"The goal of this demonstration was to create the expectation that future HALE aircraft will be refueled in flight. Such designs should be more affordable to own and operate across a range of mission profiles than systems built to satisfy the most stressing case without refueling. The lessons from AHR certainly extend beyond the HALE flight regime, and insights into non-traditional tanker concepts may offer further operational advantages."

Read on for two videos showing the Global Hawks during one of the approach maneuvers from the point of view of each UAV.