The eight climbers killed on the single deadliest day on Everest may have been victims of the "sky falling in", according to a study.

An analysis of weather patterns in May 1996 suggests the mountaineers died when the stratosphere sank to the level of the summit, 29,000ft above sea level.

The freak weather caused pressure and oxygen levels to plunge within the "death zone" - the area above 26,000ft where the oxygen is extremely thin.

Normally Everest's summit lies just below the atmospheric layer. But on May 10, the day of the disaster, there were two fast-flowing air streams, called jet streaks, moving over the mountain.