Lockheed Martin is back at square one with unmanned aerial vehicle (UAV) flight-testing after the December crash of its P-175 Polecat demonstrator, which is only now being disclosed.

The aircraft went down on Dec. 18, 2006 at the Nevada Test and Training Range, according to U.S. Air Force officials who run the range. An "irreversible unintentional failure in the flight termination ground equipment, which caused the aircraft's automatic fail-safe flight termination mode to activate" is cited by Lockheed Martin as the cause of the crash.

The company developed the aircraft for about $30 million using internal research and development funding in an effort to experiment with UAV technology while rivals Northrop Grumman and Boeing continue work on their armed UAV demonstrators for the Pentagon. However, company officials kept it a secret, claiming it was classified even though a customer has not been named. The crash was kept secret until this week, when media began making queries about Polecats status. The aircraft was beginning a new phase of flights largely focused on validating the flying wing design at altitudes in excess of 60,000 feet.

Polecat, however, never flew above 15,000 feet. Lockheed Martin officials also planned to use the aircraft to experiment with new composites manufacturing techniques, twisting strut designs to produce slightly morphing wings and ground-based vehicle and flight control work. A company statement says officials did learn from work in these areas despite the crash.

Lockheed Martin says the flight termination system "performed exactly as expected," causing the crash.