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Drifting clouds of volcanic ash have caused more than $200 million in damage to airliners in recent years, putting 1,500 lives at risk in a growing threat that has scientists warily eying the rumbling volcano on the Caribbean island of Montserrat.

Only in the past 15 years or so have people begun to recognize the danger of drifting clouds of rock that volcanoes can blast high into the air.But seven cases of engine failure on jetliners that encountered the clouds have focused attention on the problem.

Jim Lynch of the National Environmental Satellite, Data and Information Service said in an interview that because of the incidents "the whole international community . . . has become much more active. We're learning what volcanic ash looks like in satellite imagery and we're networked with (civil aviation agencies) around the world to cooperate in getting warnings out."

Perhaps the most dramatic case involved a KLM Royal Dutch Airlines Boeing 747 that flew into an ash cloud from Alaska's Redoubt volcano in 1989. The plane lost all power and dropped from 25,000 to 12,000 feet in 12 minutes before the crew could get the engines restarted.

In the high temperatures of a jet engine the ash melts into glass, Lynch explained, gumming things up and stopping the engine.

Another case in Indonesia involved a British Airways 747. The dust cloud virtually sandblasted the windscreen, forcing the pilot to partially stand up and look out a side window to land.

"It's like flying into powdered rock at 400 miles an hour" said Lynch.

And he said the powdery ash has been known to quickly clog an airliner's air vents, cutting off air conditioning needed to keep instru-ments and computers cool - as well as crew and passengers.