U.S. Navy operators lost control of an unmanned aircraft earlier this month and were unable to regain control before the aircraft entered restricted airspace around the U.S. capital.

According to a Navy statement, the incident took place Aug. 2 when, about 75 minutes into a routine test flight, an MQ-8B Fire Scout unmanned helicopter operating out of the Patuxent River test facilities in southern Maryland lost its control link with ground operators.

The aircraft then flew about 23 miles on a north-by-northwest course and entered the National Capital Region restricted airspace, part of the Air Defense Identification Zone surrounding Washington, D.C.

Incursions into the restricted airspace are not uncommon, according to the Government Accountability Office, but most violations are committed by general aviation pilots.

Navy operators shifted to another ground control station, according to the statement by Firescout program manager Capt. Tim Dunigan, and restored the control link with the aircraft, which was commanded to return to Webster Field in southern Maryland. The aircraft landed without damage or having incurred any injuries.

Although the Fire Scout has racked up more than 1,000 flight hours since December 2006, this was the first such incident to hit the program, the Navy said.

The cause appears to have been "a software anomaly that allowed the aircraft not to follow its pre-programmed flight procedures," Dunigan said in the statement. "We have identified the issue and have aircraft operating restrictions that will prevent this from happening again."

Software modification has been developed to remove the anomaly, he said.

Fire Scout flight operations were suspended following the incident pending results of an investigation.

"We are in the final stages of the investigation and plan on briefing leadership next week," Dunigan said in the statement released Aug. 25. "We anticipate resuming flight operations in early September."

Developed by Northrop Grumman, the Fire Scout is intended to provide surveillance and reconnaissance data to Navy warships, including Littoral Combat Ships and other surface combatants.