The BA274 flight from Las Vegas to London is forced to land in Montreal after a reported bomb threat
Over 312 people were onboard the jet – which has now landed in Montreal, Canada.
Dramatic pictures showed a convoy of police vehicles on the runway as the airplane landed.
Passenger Ray Connolly told Sky News: "They [cabin crew] announced that there was a report of a suspicious device."
Mr Connolly revealed the plane continued to fly for about an hour after the emergency announcement was made.
He praised the plane's staff for their "exemplary" and "exceptional" conduct during the incident.
British Airways said: "Our flight from Las Vegas to Heathrow landed safely this morning at Montreal and customers left the aircraft as normal after the captain took the decision to divert the aircraft as a precaution.
"We are looking after the customers and will provide hotel rooms for them and will rebook them to other flights as soon as we can.
"We are working with the Canadian authorities and giving them our fullest support."
British Airways refused to comment on reports of an alleged bomb threat being made against the plane.