People exit a plane from Ireland that made an emergency landing because of an unspecified threat, Wednesday, Aug. 7, 2013, in Philadelphia

A plane from Ireland makes an emergency landing because of an unspecified threat, Wednesday, Aug. 7, 2013, in Philadelphia

People exit a plane from Ireland that made an emergency landing because of an unspecified threat

PASSENGERS on board a flight from Ireland were escorted off the aircraft by FBI officials after the plane was at the centre of a bomb threat.

The US Airways flight, which took off from Shannon yesterday en route to Philadelphia and Pittsburgh. But it was surrounded by emergency vehicles as it landed at Philadelphia International Airport.

Flight 777 was ordered to land at an isolated runway before FBI and Transportation Security Administration (TSA) officials escorted passengers off the aircraft and into a fleet of waiting buses.

The 171 passengers and eight crew members were then brought to the terminal where they were isolated, interviewed and underwent screening. The aircraft’s hold was emptied of luggage and also screened with bomb-sniffing dogs brought in to search the plane.

The aircraft was later given the all clear and authorities said the threat appeared to be “unfounded”.

A spokeswoman for Philadelphia Police Department confirmed that the aircraft landed at around 2pm local time (6pm Irish time), less than half an hour after a man is reported to have phoned in a bomb threat.

America is on high alert amid an al Qaeda-linked terror threat that prompted the closing of many US embassies last week and sparked a worldwide travel warning.

However US police could not provide specific details of the threat to Flight 777 last night. “There was some type of threat made, but nothing specified,” said a police spokeswoman.

Flight 777 left Shannon at 11.34am on it's daily scheduled seven-and-a-half hour flight to Philadelphia. The same flight continues to Pittsburgh after its regular stopover in Philadelphia.

US Airways spokesman, Andrew Christie, said: “We were aware of a possible security issue with the flight and out of an abundance of caution taxied the aircraft to a remote location, where it was met by law enforcement and emergency personnel.”

FBI spokeswoman Carrie Adamowski said agents were assisting in the investigation.

The passengers had already undergone security screening at Shannon Airport, where US customs officials have their own screening facilities.

It later emerged that the crew of the US Airways flight were left sitting on the taxiway without any instructions about what to do.

Recordings of communications between the approach and tower controllers and the crew of the US Airways flight gave nothing away as to the nature of the emergency.

After landing however, the aircraft was instructed where to stop but the crew told controllers they didn't know what was going on.

“We want to talk to someone who'll tell us what's going on,” the pilot told a ground controller. The controller replied: “I can't tell you what's going on” and asked the pilot to contact the tower.

The pilot then said: “We're the aircraft sitting over here with the trucks all around it.”

The controller quickly realised what aircraft he was talking to, and told the crew to let him know if they needed anything.

The pilot of flight 777 said: “We don't even know what's going on. We need to know if we're supposed to shut down (engines) here or what the heck we're doing.”

The controller told the crew they could shut down their engines where they were stopped and told them make contact with their company.

Soon afterwards, the passengers disembarked from the aircraft via mobile stairs while their baggage was removed and placed on the tarmac.

When a threat is made against a flight, TSA officials alert the FBI and Homeland Security.

Last September a Philadelphia man called in a fake report about explosives on a flight headed to Texas. The plane was turned around and brought back to Philadelphia.

The man, Kenneth Smith, later pleaded guilty to charges of giving false information about an explosive on a plane. He was ordered to write a letter of apology to every person on the plane.

PA Media