ANCHORAGE (AP) -- For five long minutes on Dec. 15, 1989, the 231 passengers and crew aboard KLM flight 867 didn't know if they would live or die.
Volcanic ash from Redoubt Volcano killed all four of the plane's engines. The jet lost 2 miles of altitude over the Talkeetna Mountains before the crew got the engines restarted, allowing the plane to land safely in Anchorage.
Damage to the $115 million airplane was $80 million, said David Pieri, from NASA's jet propulsion laboratory at the California Institute of Technology.
About 100 people participated earlier this month in a workshop by the University of Alaska Anchorage Aviation Technology Center and the National Weather Service to learn about the dangers and avoidance of volcanic ash, according to the Alaska Journal of Commerce.
The U.S. Geological Survey says at least 15 airplanes have been damaged along North Pacific air routes since 1980 by flying through volcanic ash clouds. During that same period worldwide, another 80 airplanes were damaged by volcanic ash, resulting in hundreds of millions of dollars in damage and lost revenue.
Scientists at the Alaska Volcano Observatory in Anchorage are keeping a close watch on the Sheveluch Volcano in the Kamchatka region of Russia. The volcano, which has been quite active lately, is similar in structure to Mount St. Helens in Washington's Cascade Range. It has a growing dome inside a crater, said volcanologist Tina Neal.
''In this type of eruption, we don't get a lot of warning,'' Neal said.
If the Sheveluch Volcano erupted, the ash would likely rise quickly to 23,000 to 33,000 feet above sea level.
No airplane crashes have ever been attributed to volcanic ash.
But James Simpson, a volcano scientist at the University of California at San Diego, said as air traffic increases over popular air routes, the threat of a catastrophic crash caused by volcanic ash goes up as well.
''We've been lucky so far,'' Simpson said.
Every day thousands of passengers and millions of dollars of cargo transit the North Pacific and Russian Far East air routes where there are more than 100 potentially active volcanoes, according to the USGS.
For about four days each year in the North Pacific region, volcanic ash is present above an altitude of 30,000 feet, where most large jet aircraft fly, according to the USGS.
Pilots who fly Alaska and North Pacific air routes, some of the busiest in the world, are more aware of the dangers volcanoes pose than most, NASA's Pieri said.
''When you can sit on the end of a runway and see four active volcanoes in Cook Inlet, Alaska pilots are more aware of the danger,'' Pieri said.
Along the Alaska Peninsula and the Aleutian Islands there are more than 40 historically active volcanoes. Even greater numbers of active volcanoes are found on the Russian Kamchatka Peninsula and in the Kurile Islands.
A handful of eruptions occur annually along the 2,400-nautical-mile arc from Alaska to the Kuriles, known as the ''Ring of Fire.''
Gary Hufford, an Anchorage-based scientist with the National Weather Service, said millions of dollars have been spent in Alaska studying and forecasting volcano eruptions and implementing plans to avoid ash.
More than half of Alaska's active volcanoes are now seismically monitored. Satellite imagining of volcanoes and tracking of ash plumes also has improved, Hufford said.
Ash clouds are hard to distinguish from ordinary clouds, both visually and on radar, according to USGS. And ash clouds can travel several thousand miles in just a few days, damaging aircraft along the way.
Ed Miller of the Air Line Pilots Association International, said that of the 1,500 volcanoes worldwide, 600 are active. An average of 55 to 60 volcanoes erupt annually, and eight to 10 of those eruptions reach jetliner altitudes.
Miller, a retired United Airlines pilot, said volcanic ash can be as dangerous on the ground as it is in the air.
''When wet, it's as slippery as water on ice,'' Miller said.
He said when volcanic ash is sucked into a jet engine, the ash is heated to a hot glasslike consistency, which shuts the engine down.
''It can turn a 747 into a glider,'' Miller said.
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