It's 4:39pm, and a packed summer holiday flight from Heathrow to Valencia in Spain is descending into utter chaos. Toxic smoke has filled the cabin and the cockpit, and its 175 passengers are struggling to breathe.But that's just the start of their problems.Fearing a deadly fire that could quickly engulf the aircraft and everyone on board, the pilots have only a few minutes to try and get the plane safely on ground and avoid a catastrophe.This is the terrifying and incredible story of Flight BA422. Told by those who were on the flight, it's also captured in remarkable camera footage - filmed by the passengers as they gasped for air and faced the prospect of not getting off the plane alive.As well as compelling passenger footage, Channel 5 takes viewers into the cabin and the cockpit through vivid dramatic reconstruction, state-of-the-art special effects and first-hand testimony - as those on board experience a flight which changed their lives forever.