Air travelers across Europe are facing widespread disruption as much of the airspace in the north of the continent is closed because of a cloud of ash from an Icelandic volcano.
Civil aviation authorities in Britain, Ireland, Denmark, Sweden, Norway, and Finland have suspended entirely or partly canceled flights in their airspace.
The European air-traffic-control authority, Eurocontrol, has also decided to ground planes in Belgium, the Netherlands, and western parts of Germany.
The emergency measures are expected to last until at least tonight.
In an announcement of the closure, Britain's National Air Traffic Service said the volcanic ash represents "a significant safety threat" to aircraft.
Aviation experts say there are two primary risks involved. One is the possibility of impaired visibility, the other is the danger that ash particles can be sucked into jet engines and extinguish them.
Hundreds of flights, including trans-Atlantic flights, have been canceled or delayed. Countries in Southern and Central Europe, which have not been affected by the ash cloud, are rerouting flights where possible.
In Iceland, a volcano under the Eyjafjallajoekull glacier in the south of the country erupted on April 14, punching holes in the ice, to send a huge cloud of ash and debris 6,000 meters into the sky. Prevailing winds have brought the cloud across the North Atlantic to the European mainland.
The Icelandic Civil Defense Authority has ordered about 700 people to leave the sparsely populated vicinity of the volcano. There's been severe local flooding because of the ice melted off the glacier by the hot detritus.
The head of the local rescue effort, Rognvaldur Olafsson, told Reuters that the latest survey has shown that the glacier was now cracked for 2 kilometers of its length by the pressure from below.
Iceland is well-known for the frequency of its volcanic eruptions.
compiled from agency and BBC reports