A scared passenger on-board the British Airways flight recited the Lord's Prayer in fear as the cabin filled up with smoke shortly before landing, an ITV News editor on the flight has revealed.
Jonathan Wald said a "panic-stricken stewardess" struggled to open the plane door, leaving them stuck inside the smoke-filled plane 10 minutes after it had landed.
Mr Wald said those on board the Heathrow to Valencia flight were hurried off the plane by cabin-crew members wearing gas masks, with emergency services telling passengers to run away from the aircraft.
He was told by Spanish police that the smoke was caused by a "small electrical fire in the hold of the plane".
"We didn't receive any information about what was going on or what we should do. Most of the passengers remained calm, although there was an American passenger behind my reciting the Lord's Prayer," said Mr Wald.
"The pilot was wearing a gas mask and managed to make a steady, controlled landing even though his vision would have been seriously impaired by the smoke in the cockpit.
"We then remained in the cabin for around 10 minutes after landing as a panic-stricken stewardess struggled to open the door.
He added: "As soon as she did, cabin crew, some wearing gas masks, shouted it was an emergency and we had to evacuate immediately.
"We went down the stairs and emergency services on the ground told us to run away from the plane."
Three passengers were treated for smoke inhalation, while 16 others were treated for anxiety and chafing suffered when they slid down inflatable emergency slides.
British Airways said in a statement that flight BA422 had "experienced a technical issue on its landing approach into Valencia".
The airline added: "All our customers were evacuated safely by our crew and met by the airport's emergency services.
"There were 175 customers on board the flight, with six cabin crew and two pilots.
"Three customers were taken to hospital as a precaution and have since been discharged.
"The safety of our customers and crew is always our highest priority.
"In addition to our team on site, other British Airways team members have arrived in Valencia to help our customers and our local airport partners with anything they need."
Gayle Fitzpatrick, from Glasgow, who was on holiday with her husband Stephen, described the moment smoke entered the plane’s cabin.
She said: "It was very scary. The flight was just ending, and with 10 minutes to go the flight started descending rapidly as smoke started to fill the cabin.
"A detector was going off saying the cabin was filling with smoke. It was like a horrible white acrid smoke.
"There was chat it was an air conditioning unit.
"There were no communications from the crew, some of which started to wear full oxygen masks and protective fire wear.
"Eventually they managed to open the emergency doors and told us to go down the chutes.
"There were fire engines waiting and then we were all ushered into a bus then to the airport.
"We are still waiting to hear what happened. People were crying and hyperventilating. It was genuinely scary.”
She added: "We were not told it was an emergency until we had landed and they were trying to open the cabin doors for passengers to jump down the chutes."
Mrs Fitzpatrick claimed passengers had been stuck at the airport for at least two hours "without any information at all".
She said groups of people had since been told they could go and collect items from the plane.
Another passenger took to Twitter to share photos of the incident, saying: "terrifying experience on flight to Valencia. Felt like horror film. Thankfully everyone safe. Flight filled with smoke and had to be emergency evacuated."