SEATTLE -- Boeing's A160T Hummingbird unmanned rotorcraft flew for 18.7 hours on an overnight flight May 14-15, setting what the company believes is a world endurance record for a UAV in its weight class.

The flight, which was accomplished at the U.S. Army's Yuma Proving Ground in Arizona, was one of two key performance tests set by the Defense Advanced Research Projects Agency (DARPA) to mark the completion of the initial development phase. The other major test, a series of hover-out-of-ground-effect (HOGE) demonstrations at altitudes between 15,000-20,000 feet, was successfully completed on May 9, Boeing says.

The HOGE flight lasted 2.9 hours, including hovering for more than seven minutes, while the more recent endurance flight involved carrying an internally mounted 300-pound payload to altitudes up to 15,000 feet. Boeing originally planned to attempt both milestone flights late last year, but was thwarted when a test aircraft crashed on Dec. 10 near the company's Victorville, Calif., test site.

Boeing subsequently modified software and diagnostics in the flight control system after its accident investigation board (AIB) determined that sensor data in the flight computer stopped being updated in midflight. Since resuming flight-tests the A160T has reached a speed of 142 knots, marked an eight-hour flight carrying more than 1,000 pounds of payload and flown a 12-hour flight carrying more than 500 pounds. All flights were accomplished using “a fraction of its maximum fuel capacity,” the company adds.

The goal of the A160T development, which is supported by the U.S. Army Aviation Applied Technology Directorate and U.S. Naval Air Systems Command along with DARPA, is to demonstrate the potential for a UAV that combines the operational advantages of a helicopter with the payload and endurance of a fixed-wing aircraft. Further development flights will explore the flight envelope to higher speeds and altitudes as high as 30,000 feet.

Boeing has meanwhile submitted an application to the National Aeronautic Association, the U.S. sanctioning body for the Fédération Aéronautique Internationale (FAI), to officially claim the world record.