Airliners Threatened by Drifting Volcanic Ash Clouds : Hazards: Airborne debris from eruptions has caused more than $200 million in damage and put 1,500 lives at risk in recent years, scientists warn.

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 eyeing the rumbling volcano on the Caribbean island of Montserrat.

Only in the last 15 years or so have people begun to recognize the danger of drifting clouds of rock that volcanoes can blast 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 restart the engines.

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.

The powdery ash has been known to quickly clog an airliner’s air vents, he said, cutting off air conditioning needed to keep instruments and computers cool--as well as crew and passengers.

More than 80 airliners have been damaged by drifting clouds of ash over the last 15 years, including the seven instances when engines failed, the U.S. Geological Survey reports. The agency said those seven instances resulted in damage of more than $200 million to the airliners and endangered about 1,500 passengers.

Now, the Geological Survey, National Oceanic and Atmospheric Administration’s satellite service, and Federal Aviation Administration work together to monitor the threat of explosive eruptions and notify pilots when danger threatens. Worldwide cooperation is provided by the International Civil Aviation Organization and World Meteorological Organization.

Because the Montserrat volcano is known to be threatening, federal observers check satellite pictures several times a day for suspect clouds that could indicate ash in the air. Several potentially active volcanoes around the world are being monitored regularly.

The Montserrat volcano has no history of explosive blasts that could shoot ash to dangerous altitudes, Lynch said. But it is being watched because, when even a small eruption begins, a volcano can sometimes blast dust and debris into the air.

There is plenty of air traffic in the region and the volcano is located between the heavily traveled air routes connecting New York to Rio de Janeiro and New York to Buenos Aires.

Since ash clouds can look a lot like a thunderstorm, Lynch said, observers try to verify eruptions with researchers on the ground. Currently, U.S. Geological Survey scientists are at Montserrat monitoring the volcano.

Once ash is spotted, the weather observers send out a “notice of a significant meteorological event.” The Federal Aviation Administration relays this as a warning “notice to airmen.” Computers can speed the word around the world.