British fighter jets escorted the plane to Glasgow Prestwick Airport yesterday after the discovery of a note threatening to set it on fire, authorities and eyewitnesses said.
Following a police search of the Boeing 777 plane overnight, it was allowed to continue its journey.
"Officers from Police Scotland have carried out an extensive search of the aircraft resulting in no suspicious items being found," a spokesman for the service said.
"Passengers and crew are now aboard and the aircraft is continuing its flight to New York.
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All 326 passengers had been taken off the plane.
The alarm was raised when a passenger, BBC New York producer Nada Tawfik, said she told plane crew that she had found a note in the toilet sink that read "I'll set this plane on fire."
Tawfik told the broadcaster that the message was scrawled in pencil on a napkin and that it also pinpointed a seat number.
"Either someone has a very bad sense of humour or, you know, it's very scary," she said.
Britain is on high alert as world leaders including US President Barack Obama and Russian President Vladimir Putin converge on Northern Ireland for the G8 summit, which begins tomorrow.
Police Scotland said the flight had been diverted following the discovery of a suspicious note on the plane.
Prestwick Airport, on the southwest coast of Scotland, and is one of the last places planes can land, if necessary, on the transatlantic route from Europe to North America.