The threat was phoned in by an unknown male
(Philadelphia, PA) -- Police and Homeland Security agents are conducting a security sweep of a plane that landed at Philadelphia International Airport this afternoon due to an "unsubstantiated" threat. US Airways flight 777 originated in Ireland and was scheduled to arrive in Philly at 2:05 p.m., but touched down a few minutes early. All passengers have been taken off the plane and loaded onto buses. NBCPhiladelphia quotes police as saying the threat was phoned in by an unknown male.