An investigation has been launched into why a Ryanair plane suddenly lost cabin pressure.

Passengers were terrified when the Boeing 737-800 was forced to descend quickly before diverting to a French airport while en route from Bristol to Girona in Spain.

They included Arctic explorer Pen Hadow, whose son Wilf, nine, was among 16 passengers hospitalised with ear problems after flight FR9336 landed safely at Limoges.

Mr Hadow said passengers feared for their lives, oxygen masks did not work properly and that there were no immediate announcements to passengers about what was happening.

He said: "There was a sudden drop in temperature and a rush of cold air. 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. It was incredibly cold."

He added: "The next thing the oxygen masks were dropping. My highest priority was to get a mask on to my son who was sitting next to me in a bemused and frightened state.

"We were descending for about five minutes from what I assume was 30,000 or 40,000ft to 8,000ft. As we landed we saw fire engines every quarter of a mile down the runway.

"It was obvious to me that there was depressurisation in the cabin but there was no announcement and no evidence of the cabin crew for most of this experience. Why on earth didn't they give a few more calming words to the passengers?"

Mr Hadow said a number of oxygen masks inside the cabin had failed to inflate.

But Ryanair chief executive Michael O'Leary said: "The oxygen masks were working, the correct safety procedures were followed.

"The first thing we do in these situation is divert to safety, take the safety first option. We have to require that the pilots and the cabin crew also deploy their oxygen masks.

"They can't be making passenger announcements when they have their oxygen masks on. As the passengers confirmed, the pilot did make an announcement once he got down to 8,000ft, where it is safe to take the oxygen masks off, that they were diverting to Limoges."

© Independent Television News Limited 2008. All rights reserved.