An unmanned Army surveillance blimp broke loose from its moorings in Maryland and floated over Pennsylvania for hours Wednesday with two U.S. fighter jets on its tail, triggering blackouts across the countryside as it dragged its cable across power lines.

The bulbous, 240-foot helium-filled blimp finally came down near Muncy, a small town about 80 miles north of Harrisburg.

The North American Aerospace Defense Command in Colorado said the blimp detached from its station at the military’s Aberdeen Proving Ground in Maryland at about 12:20 p.m. and drifted northward, climbing to about 16,000 feet.

The F-16s were scrambled from a National Guard base at Atlantic City, New Jersey, according to NORAD. At the Pentagon, Defense Secretary Ash Carter did not say what the two fighter jets might be asked to do or whether he considered it a threat to aviation.

Witnesses reported seeing the blimp drifting in a sparsely populated area. Its tether was snapping power lines.

The local electric utility, PPL, reported about 20,000 customers without power in the area, and Bloomsburg University canceled classes because of the outage.

The blimp is the kind used extensively in the Iraq and Afghanistan wars to provide ground surveillance around U.S. bases and other sensitive sites. It is tethered to the ground when in use.

“My understanding is, from having seen these break loose in Afghanistan on a number of occasions, we could get it to descend and then we’ll recover it and put it back up,” Carter said. “This happens in bad weather.”

As the blimp drifted away, Federal Aviation Administration officials worked with the military to ensure air traffic safety.

The aircraft is known as a Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, or JLENS, and can be used as part of a missile defense system.

It was not immediately clear how the blimp came loose.

(AP)