The Eyjafjallajokull volcano, one of Iceland's largest, had been dormant for nearly two centuries before returning gently to life in the late evening of March 20, 2010, noticeable at first not by any great seismic activity but by the emergence of a red cloud glowing above the vast glacier that covers it.

In the following days, fire fountains jetted from a dozen vents on the volcano, reaching as high as 100 meters, according to the Institute of Earth Sciences at the University of Iceland. That spectacular show, along with lava flows up to 20 meters thick, and "lava falls" to the volcano's northeast, turned it into a full-fledged tourist attraction.

The volcano seemed to return to somnolence. Then on April 14, 2010, an explosion sent clouds of ash soaring as high as 11,000 meters, disrupting air traffic in Northern Europe, with ripple effects far beyond. Travel chaos across the globe deepened as the vast, high-altitude plume of volcanic ash spread farther across northern and central Europe, forcing aviation authorities to close more airspace and ground more airplanes to forestall damage to jet engines.

By the afternoon of April 16, most of Europe's major airports - crucial hubs for international travelers - were closed. Thousands of flights were canceled, stranding or delaying millions of passengers across airports from North America to Asia. It was the worst peacetime air travel disruption in history, a nearly weeklong halt in flights that cost airlines hundreds of millions of dollars and raised questions about Europe's ability to respond coherently to a crisis.

Aviation authorities in Europe agreed to carve airspace above the continent into three zones - one closest to the volcano where air traffic would be completely restricted, another zone with partial flight restrictions, and a third zone, free of ash, where flights could resume completely. On April 20, a new cloud of volcanic ash was headed toward Britain, increasing uncertainty about the prompt return of air traffic to parts of the British Isles.

Source : www.nytimes.com