A number of dangerous incidents involving volcanic ash interfering with airplane engines caused the United Nations’ International Civil Aviation Organization to establish the Volcanic Ash Warning System, a global system of nine centers that uses computer modeling to forecast the path of ash clouds and alerts aviation services if necessary. The VAWS alerted civil aviation authorities in Europe after Eyjafjallajokull’s eruption.
In 1982, a British Airways Boeing 747 flying over Indonesia flew through an ash cloud produced by the eruption of Mount Galunggung. The plane, flying at 37,000 feet, with 247 passengers and 15 crew on board, lost all four engines. The crew descended rapidly out of the cloud and managed to restart three engines, eventually landing safely at Jakarta airport. A number of similar incidents occurred in the 1980s as well.
Volcanic ash presents a serious threat to jetliners flying at high altitude. The ash, which has a consistency similar to talcum powder, can be invisible and often doesn’t show up on either ground-based radar or the weather radar systems on board jetliners, according to Paul Hayes, director of safety at Ascend Ltd., an aviation consulting firm in London.
The first warning a flight crew would have of volcanic dust is a sulfurous smell from the plane’s air-conditioning system and possibly electrical discharges, known as “St. Elmo’s fire,” on some external surfaces of the plane, Mr. Hayes said.
As of late Thursday, the volcano was still pumping out new ash, and civil aviation authorities across Europe worried that the volcano would continue disturbing air traffic for months.
“Volcanoes are notoriously irregular in their behavior,” said Pall Einarsson, professor of geophysics at the University of Iceland. “If there is any rule about them it is: There is no rule.”
—Mike Esterl and Doug Cameron contributed to this article.
A look at some airports experiencing moderate or severe delays. Plus, previous ash cloud incidents. Click to enlarge image.