The US Federal Aviation Administration said the event was over after ordering all departures from Philadelphia International Airport (PHL) grounded due to a bomb threat.
The FAA issued a ground stop advisory for the airport shortly after 7 p.m. local time (0000 GMT), saying there was a bomb threat. About 30 minutes later, the FAA said the security incident had been resolved and that normal operations had resumed.
The ground stoppage was due to a "situation requiring the assistance of the Philadelphia Police aboard a plane," a police spokesperson said in an emailed statement.
The plane has been cleared for takeoff, and the ground stoppage has been lifted, the spokesperson added.
Bomb threats in other airports
There were reports of bomb threats at other US airports earlier this month that were also cleared without incident.
Operations at the Reagan Washington National Airport faced a brief halt in early November due to a bomb threat against a United Airlines UAL.O plane. The FBI said at the time it had responded to the report and found nothing hazardous.
On the same day, a Delta DAL.N flight from LaGuardia International Airport was evacuated before takeoff after reports of a bomb threat.