The TAP Air Portugal flight from London to Lisbon made an emergency landing in Spain after the patient was found to be unconscious.
The plane touched down at Santiago de Compostela Airport in the country’s northwestern Galicia region.
Staff at the airport had notified the emergency services and paramedics were dispatched to the scene.
After the flight landed, the medical staff tried to revive the man, but their efforts were in vain and he was pronounced dead at around 9.30pm on Friday (May 6).
His initials were given as I. S. Y. and he was 71 years old.
No further details about him were reported.