The passenger, an 80-year-old man, reportedly suffered a heart attack as the plane cruised to Thailand.
Cabin crew tried to carry out CPR for 40 minutes, but the man died an hour before landing, according to AirLiveNet.
A British Airways spokesman told Daily Star Online this evening: “Our thoughts are with his family and friends.”
The flight landed in Thailand last night 45 minutes later than scheduled, according to FlightRadar24 data.
It’s return flight to London today was also delayed by two hours.
The plane the incident took place on was a Boeing 777 which departed Heathrow last night at 5.10 pm.