The BA766 flight to Oslo in Norway made a U-turn to the UK capital this afternoon after encounting a “technical problem”.
It was already flying over the North Sea when the pilot reportedly made a “7700” squawk alert – which means a general emergency.
The plane turned back at around 2.30pm before circling outside Greater London to dump fuel.
It then made the final landing approach for Heathrow at 3.45pm before touching down at 4pm.
Data on FlightRadar24 shows the plane taxied to the gate straight after landing, indicating a safe landing.
It remains unknown why the plane declared an emergency, although AirLiveNet reports it was a “precautionary” measure.
The Airbus A321 plane had left Heathrow at 1.47pm this afternoon – 47 minutes later than scheduled – and was due to land in Oslo at 4.15pm.