A spokesman with the Ottawa Paramedic Service told Fox News the agency responded to the incident around 2:18 a.m. and said the passenger, who is a man in his 50's or 60's, suffered a cardiac arrest during the flight, which prompted the pilot to make an emergency landing in Ottawa, Canada.
He said physicians on board the plane tried to revive the man with a defibrillator and with medication but the patient did not respond to treatment.
Paramedics tried to save the man once the plane landed but he was pronounced dead while he was being transported to the hospital.
The airline said in a statement to Fox News: "American Airlines flight 80, from Dallas Fort Worth to London Heathrow, diverted to Ottawa due to an ill passenger."
"Our crew and a fellow passenger provided medical care until the flight landed at 2:28 a.m. local time this morning, where medical personnel met the aircraft.”
"Flight 80 re-fueled, and re-departed Ottawa at 4:36 a.m. local time, and is currently en route to London," the statement concluded.
The Ottawa Paramedic Service spokesman told Fox News that any other information about the passenger will not be released until next of kin are notified.