A British Airways flight has been evacuated after smoke filled the cabin shortly before landing.
The airline confirmed there was an “incident” on flight BA422 which departed London Heathrow on Monday and has now landed in Valencia.
Passenger Gayle Fitzpatrick, from Glasgow, told PA a “horrible white acrid” smoke filled the cabin about 10 minutes before its scheduled landing.
BA has apologised to passengers on board the aircraft, an Airbus A321.
It added that its staff were assisting customers in the airport terminal.
Pictures have emerged on Twitter of what appears to be a plane cabin filled with smoke.
Passenger Lucy Brown tweeted that the “terrifying” experience felt like a “horror film”.
A BBC producer at Valencia airport was told by a member of staff on the ground that there was a “fire in the motor” of the plane.
Mrs Fitzpatrick, who was on holiday with her husband Stephen, said fire crews were waiting on the runway when the plane landed and passengers were directed to the terminal.
“There were no communications from the crew, some of which started to wear full oxygen masks and protective fire wear,” she said.
“Eventually they managed to open the emergency doors and told us to go down the chutes.”
She added: “People were crying and hyperventilating. It was genuinely scary.”
In an email to affected passengers British Airways said it was “sourcing an alternative aircraft” to operate flights back to London.
Travellers who have been delayed overnight have been given free accommodation at a local hotel, BBC News has been told.