A massive surveillance blimp in the United States has broken loose from its mooring in Maryland and is floating toward Pennsylvania with two US fighter jets following it.
The so-called JLENS aerostat, which is nearly the length of a football field, detached from its mooring in Aberdeen Proving Grounds at around 12.20pm (local time), the North American Aerospace Defense Command (NORAD) said in a statement.
Two F-16 fighters were monitoring the helium-filled blimp as it floated northeast of Washington at an altitude of about 4875 metres.
"NORAD officials are working closely with the FAA (Federal Aviation Administration) to ensure air traffic safety, as well as with our other interagency partners to address the safe recovery of the aerostat," NORAD said.
It was not immediately clear how officials planned to recapture the blimp.
JLENS blimps carry powerful radars that can protect an area about the size of Texas from airborne threats including unmanned aircraft, cruise missiles and other objects.
The aerostats normally fly at about 3000 metres.