Passengers on board flights from the UK to San Francisco are being diverted elsewhere after a plane crash-landed at the city's airport.
Many more are believed to have been injured, with photographs showing passengers escaping the burning wreckage of the plane by jumping down the emergency inflatable slides to safety.
A spokeswoman for BA said its two flights which left Heathrow today had been diverted to Seattle and Vancouver airports.
A Virgin Atlantic spokeswoman said it operated one daily flight between Heathrow and San Francisco. She added: "Currently our flights to and from San Francisco are operating as scheduled. We advise passengers to continue to check Flight Status for the very latest information."
Television footage of the incident showed the Boeing 777 lying on the runway with thick plumes of smoke pouring out from it, while debris was strewn across the tarmac.
The top of the fuselage appeared to be burned away while the entire tail was missing.
Up to 300 passengers were thought to be on board, with images showing many of them being tended to by emergency services at the scene.
A spokeswoman for San Francisco General Hospital told a local radio station that 10 passengers had been admitted including two children, with all in critical condition.