WASHINGTON  The skies over the nation’s capital are crowded with presidential aircraft, military flyovers and the Delta shuttle, but this month a strange new bird was briefly among them: a United States Navy drone that wandered into the restricted airspace around Washington before operators could stop it.

Navy spokesmen could not say Wednesday if anyone on the ground was alarmed by the drone  officially an MQ-8B Fire Scout Vertical Takeoff and Landing unmanned aerial vehicle  which looks like a small windowless helicopter and was flying at 2,000 feet. The Navy did say that the drone got within 40 miles of Washington before operators were able to re-establish communication and guide it back to its base in southern Maryland.

Still, the Aug. 2 incident resulted in the grounding of all six of the Navy’s Fire Scouts as well as an inquiry into what went wrong. The Navy is calling the problem a “software issue” that foiled the drone’s operators.