A British Airways plane has made an emergency landing after smoke engulfed the entire cabin.
Tourists are seen using the evacuation slide on the runway at Valencia, Spain, in a video shared online. Three people were rushed to hospital.
In another clip, thick grey smoke is seen in the cabin itself.
One frightened passenger's dad, who was not on board, told Mirror Online: "Apparently they flew for 10 minutes with the cabin full of smoke, no info from crew and oxygen masks failed to release."
Lucy Brown, who was on board with her four terrified children, exclusively told Mirror Online: "We are thankful everyone is safe but, had this happened half an hour earlier, it might be a different story.
"There was a horrible smell. People were almost choking."
Flight number BA422 is thought to have been affected - which left Heathrow Airport this afternoon.
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Mrs Brown, an associate dean at London College of Communication, added: "They were struggling to open the emergency doors because they were that stiff.
"Air hostesses were trying to communicate but you couldn't see anything.
"It happened suddenly, about ten minutes before we were due to land. The plane was pretty full too, with lots of families and young children. My kids were in tears."
She also shared dramatic photos online of smoke filling the cabin.
Another photo mum shows passengers leaving the plane.
She tweeted: "Terrifying experience on flight to Valencia. Felt like horror film.
"Thankfully everyone safe. Flight filled with smoke and had to be emergency evacuated."
In a further post, the lecturer added: "So pleased to be off the plane. Kids never want to fly again!!!"
Another passenger tweeted: "My husband and I were on the flight. Genuinely scary experience.
"No comms regarding what was happening....still waiting to hear. We are safe, but shaken."
A spokesman for British Airways said: "We can confirm that British Airways flight BA422 from Heathrow to Valencia has been involved in an incident today.
"The aircraft, an A321, has landed and all customers and crew have disembarked.
"British Airways teams are assisting customers who are in the airport terminal."
The plane left Heathrow Airport earlier today and Valencia, on the east coast of Spain, was always its intended destination.
No injuries have been reported.
