A British Airways flight from London to Seattle was forced to turn around after it declared a mid-air emergency.
The flight was just under two hours into an eight-hour flight to the city, in the North West of the US.
A British Airways spokesperson said the flight's pilots had encountered a "technical problem", although reports suggested there was a problem with oxygen in the cabin while it was flying over Scotland, just to the north west of Edinburgh. As it passed over the Midlands, the Boeing-777 was said to be flying at "barely 17,000ft".
Twitter users posted images of the low-flying aircraft:
The flight was given priority to land at Heathrow on what was described as a "very busy afternoon".
A spokesperson for British Airways said:
The aircraft has landed safely. Our highly trained pilots returned to Heathrow as a precaution after a suspected technical fault. The safety of our customers and crew is always our top priority.