Authorities in the US state of Pennsylvania are reported to have secured an unmanned Army surveillance blimp that tore loose from a base in Maryland.
The blimp detached at about 12.20pm local time on Wednesday and drifted north into Pennsylvania, the Pentagon said.
Two F-16 jets from the Atlantic City Air National Guard Base in New Jersey were dispatched to monitor the blimp.
The craft was tracked travelling at an altitude of about 16,000ft (5,000m). The Pentagon said the blimp was descending.
Local media have attributed power outages in the area to the free-floating blimp's tether hitting power lines.
Pennsylvania-based electric utility PPL said about 20,000 customers were without power, but it was unclear how many could be attributed to the runaway blimp.
Witnesses reported seeing the blimp drifting in area north of Harrisburg, its tether snapping power lines.
US aviation officials said they were working with the military to ensure safe air travel in the area.
The high-tech blimp is equipped to help detect a missile attack, the North American Aerospace Defense Command (NORAD) said.
Update: JLENS aerostat drifting northward & has descended near the ground. Anyone seeing the aerostat notify law enforcement & remain clear
— NORAD & USNORTHCOM (@NoradNorthcom) October 28, 2015
