Black box found in Pennsylvania

The flight data recorder from United Airlines Flight 93, which crashed in Pennsylvania killing all 45 people on board, was found at the crash site, transport officials said.

The black box could shed light on what happened during the flight after the plane left Newark bound for San Francisco.

It was the only hijacked plane not to hit a US landmark building.

US airspace, closed since the attacks, was reopened at 1100EDT (5pm Irish time), with airports being allowed to resume operations on a case-by-case basis.

But by late Thursday the authorities had ordered the closure of all New York's airports due to what officials said was "FBI activity."