A massive aerial blimp equipped with radar to track military threats has come loose, the Pentagon said, and now is being accompanied by two fighter jets as its drifts north, 16,000 feet in the air.

The blimp, part of the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System (or JLENS), came loose around 12:20 p.m. at Aberdeen Proving Ground in Maryland, according to a DoD statement.

The FAA now is tracking the unmanned craft to ensure flight safety, in addition to the F-16 fighter jets alongside it. It is unclear whether officials were prepared to shoot the blimp down. According to The Baltimore Sun, it was trailing approximately 6,700 feet of cable.

JLENS uses two tethered aerostats—each 74 meters long and filled with 590,000 cubic feet of non-flammable helium—to detect threats ranging from drones and cruise missiles to tanks.

It is an Army development that, according to a March 2014 Government Accountability Office report, cost an estimated $2.78 billion.

The blimp has flown above Aberdeen Proving Ground for roughly a year, defense officials said. They could say how it came loose.

—Nancy A. Youssef