Terrified passengers suffered damaged eardrums and nosebleeds as a Ryanair jet descended 20,000ft in just five minutes before making an emergency landing in France.
Screaming and crying erupted aboard flight FR9336 from Bristol to Girona in Spain as the aircraft lost cabin pressure and 168 passengers grappled frantically for oxygen masks.
Afterwards, 16 passengers were taken to hospital where staff said most injuries were caused by a loss of cabin pressure combined with the sudden loss of altitude as the pilot brought the plane down to 8,000ft in mid-flight.
Passengers in such situations often refer to planes "plummeting'' or "dropping like a stone''. But in practice, pilots descend only as quickly as is safe, so as not to exceed the plane's maximum speed.
Ryanair has confirmed the flight, which left Bristol late on Monday headed for Girona, 100km from Barcelona, was forced to make an unscheduled landing in Limoges International Airport due to a loss of cabin pressure.
Limoges hospital spokesman Rene Chaffard said: "Many of those brought to us suffered nose and ear pain as the pressure in the cabin was lost.
"The ear injuries were then aggravated by the swift loss of altitude. Those brought to us had severe headaches, nosebleeds and damaged eardrums.
"Most were also suffering from shock. But thankfully they are all expected to make a full recovery."
All the injured travellers were discharged yesterday morning and continued their journey to Girona by coach. British Arctic explorer Pen Hadow, who was aboard the plane, said the incident "was traumatic for many involved".
He added: "Suddenly there was a roar of wind, a rush of cold air, the oxygen masks dropped, you didn't know what was going on."
"You think to yourself, 'God, is there a hole in the aircraft?' It actually felt like someone had opened a door at the back of the aircraft," he said. "It was incredibly cold. My highest priority was to get a mask on to my son who was sitting next to me in a bemused and frightened state. Mine wasn't filling up with oxygen and neither was my son's.
"He was hyperventilating. I looked at the lady on my left and hers hadn't filled up either.
"From where I was sitting I could see about 20 masks and only a few of them were inflating.
"It was extremely variable as to who got oxygen in their masks, and the cabin crew didn't seem to know what to do."
Hadow, who in 2003 became the first person to reach the North Pole unaided from Canada, said: "I was surprised there seemed to be no communication between the pilot and the flight attendants because they didn't seem to know what to say and do."
"There was absolutely no communication from the flight crew and that added to people's extreme fear."
Another passenger described hearing a "thumping noise, then a rush of very cold air through the cabin. People began shouting out in fear.
"When something like that happens, people obviously think they are going to die.
"Everyone began reaching for their masks, babies started crying, people clung on to each other. Some were being sick. It was a truly frightening moment."
But Ryanair chief executive Michael O'Leary dismissed passengers' complaints about the masks.
"Passengers sometimes misunderstand... they expect a surge of oxygen when in actual fact there is a steady stream of oxygen," he said.
"The oxygen masks were working and the correct procedures were followed. As soon as the captain got the plane down to 8,000ft he did make the appropriate announcement that they were going to divert to Limoges for safety reasons.
"This is always a traumatic experience for passengers but... the crew dealt with it appropriately."
Ryanair released a statement saying its engineers had inspected the five-year-old Boeing 737-800, which had been serviced a month ago on July 24, and that the oxygen masks had been working.
Irish and French aviation authorities have been notified of the incident and a full investigation will be undertaken.
Loss of cabin pressure is not infrequent on passenger planes but occasionally it can have fatal consequences. Three years ago, a pressure problem led to a Boeing 737 crashing in Greece with the loss of 121 lives.
Any sudden loss of cabin pressure automatically results in oxygen masks descending. It is vital that pilots then don their masks within about 30 seconds so they can take the aircraft down as quickly and as safely as possible to between 8,000ft and 10,000ft, where the air is breathable.
Should cockpit crew masks not be put on straight away, the pilots will quickly lose consciousness -- with deadly results.