Paris ? A cloud of ash hovered over Europe on Friday, casting a pall over an interwoven world.

Made up of microscopic particles as hard as a knife’s blade, the dust cloud coughed up by an Icelandic volcano crept across the industrial powerhouses of Europe, into the steppes of Russia and as far south as Hungary.

It left behind stranded travelers, grounded cargo flights, political confusion and even fears the cloud of grit settling on Earth will endanger the lungs of children, asthmatics and others with respiratory ailments.

The volcano in southern Iceland’s Eyjafjallajokull glacier sends ash into the air just prior to sunset Friday. Thick drifts of volcanic ash blanketed parts of rural Iceland on Friday as a vast, invisible plume of grit drifted over Europe, emptying the skies of planes and sending hundreds of thousands in search of hotel rooms, train tickets or rental cars.

How long it lasts and how far it spreads depends entirely on two unpredictable events: Whether the volcano beneath Iceland’s Eyjafjallajokull (ay-yah-FYAH’-plah-yer-kuh-duhl) glacier keeps pumping tons of dust into the air and what wind patterns do.

The invisible cloud could split, reaching down into northern Italy, and perhaps break apart over the Alps. Scientists say the volcano could continue erupting for months, with more chaos ensuing with each big belch of basalt powder and gas.

“It’s going to be a mess,” said volcanologist Michael Rampino of New York University. “It’s a menace to air traffic, just sitting there, waiting to go off.”

Henry Margusity, senior meteorologist for AccuWeather.com, predicted the jet stream winds will continue picking up dust over Iceland and carry it to Britain and Europe “like a spray can of ash” through next Wednesday.

Change of plans

Is it a first? The devastating 19th-century eruption of Indonesia’s Krakatoa island was bigger. In ancient times, Mount Vesuvius buried an entire city and in the 17th century, a series of eruptions from Peru to the South Pacific blocked the sun’s energy and sent the Earth’s temperatures plunging.

But in this era of global trade crisscrossing the planet by air, the Icelandic eruption has implications that underscore the particular vulnerabilities of the modern world.

A new iPad helped Norway’s Prime Minister Jens Stoltenberg keep in touch with his government while he was stuck in Switzerland, where he ended up after trying to fly home from the U.S.

With German air space closed, a flight carrying five German soldiers wounded in Afghanistan was diverted to Turkey; U.S. medical evacuations from Iraq and Afghanistan went directly to Washington.

Airline cancellations also brought personal anguish.

Anissa Isker arrived at Charles de Gaulle airport early Friday in hopes of taking her 8-year-old son Ryan, who has a rare genetic disease and uses a wheelchair, to Miami for treatment that could help him walk.

The hard-to-schedule treatment costs $3,000, a sum she is afraid she will lose if they can’t leave this weekend.

“I think it’s going to be tough, especially with my little one. When I told him we cannot leave, he got nervous,” Isker told AP Television News. “Because he wants to go, he has made up his mind and he cannot understand.”

Potentially lifesaving organs, too, were stuck in transit.

All organs that usually get flown out to patients were instead being distributed to those within driving distance.

“Hearts, lungs and livers, which are normally transported by air, are now delivered regionally and by ground travel,” said Nadine Koerner, a spokeswoman for the German Foundation for Organ Transplant.

The World Health Organization warned the ash could cause breathing problems. Europeans, especially those with respiratory ailments or asthma, should try to stay indoors if the ash starts settling.

“We’re very concerned about it,” said WHO spokesman Daniel Epstein. “These particles when inhaled can reach the peripheral regions of … the lungs and can cause problems.”

Other experts, however, weren’t convinced the volcanic ash would have a major health effect. Ken Donaldson, a professor of respiratory toxicology at the University of Edinburgh, said volcanic ash was much less dangerous than cigarette smoke or pollution.

With planes in Norway grounded and trains booked up, British comedian John Cleese resorted to a $5,100 taxi ride to Brussels from Oslo, where he had taped an appearance on a Norwegian talk show Thursday night. From there, he planned to go by train to London, his publicist said.