Volcanic ash affects airplanes, weather, sunsets  — NEW YORK
(AP) - In 1989, all four engines of a Boeing 747 over Alaska
conked out after it flew into a cloud of volcanic ash. The crew
was able to restart them, but incidents like that dramatize why
hundreds of flights every year are diverted around the razor-
sharp debris.  A volcano can blow immense amounts of material
into the sky, making the weather cooler and producing
spectacular red and orange sunsets. But Thursday's disruption of
air travel underlines what airborne ash can mean for jetliners.
Such a huge effect on airline schedules is unusual, because ash
plumes usually appear well away from the most crowded airspaces.
This week's eruption in Iceland blew debris over Northern
Europe, threatening most routes from the East Coast to Europe.
Volcanic ash can stay aloft for days and travel far. Of the more
than 20 aircraft damaged by ash from the 1991 eruption of Mount
Pinatubo in the Philippines, most were flying more than 600
miles from the volcano.  Th