European transport ministers on Monday declared most of the skies of Europe safe for flying despite the ongoing plume of volcanic ash in the sky from an Icelandic volcano.

But if University of Pittsburgh volcanologist Dr. Ian Skilling, an expert on Icelandic volcanoes, had to fly to Europe this week, he wouldn't go.

"Not right now, no," said Dr. Skilling, who has spent most of the last two decades studying how Icelandic volcanoes interact with ice. "I'd still be pretty worried."

The transport ministers' decision Monday "is obviously a response to pressure from the airline industry," he said. "It probably does make economic sense for the airlines, but they're pushing the safety margins."

Though he normally does his work on Icelandic volcanoes in relative anonymity, thanks to the ongoing eruption of Eyjafjoell volcano that began Wednesday he has been a go-to expert for media over the last week, doing a dozen interviews, including two with British reporters.

But it's impossible to give a clear-cut answer to the stock questions he has been asked by reporters and government officials over the last week: When will it stop erupting? And when can planes can start flying safely again in northern Europe?

"The answer is basically that no one has any idea whatsoever," said Dr. Skilling, 47, a British native who came to work at Pitt in 2002 and will return to Iceland this July. "There's no shortage of molten rock and water that could let it go on for months or more than a year."

Dr. Skilling studies Icelandic volcanoes -- working at two sites north and south of the current eruption -- in hopes that they can tell us about climate change over the last 2.5 million years.

There's ample historical evidence of other Icelandic volcano eruptions that went on for months or more than a year, though none in modern times has previously affected international air travel the way this eruption has, Dr. Skilling said.

He noted that Laki, perhaps the best known and most devastating of all Icelandic volcanic eruptions, started in June 1783 and lasted eight months.

Laki's eruption pumped perhaps a 100 times more ash into the sky than the current one and resulted in global weather shifts that killed upwards of one-third of Iceland's population from both acid rain and the starvation that followed the destruction of Iceland's sheep industry. It also killed thousands more in England when the poisonous cloud drifted there.

Benjamin Franklin was in Europe that summer and noted the unusually cold and moist weather "and may have been the first person to have tied volcanic eruptions to weather patterns," Dr. Skilling said.

While this eruption is not on the same scale, Dr. Skilling is worried that other historical lessons about volcanoes have not been well learned.

"Everyone in the field is worried right now that the airlines are getting so itchy losing millions of dollars a day that officials might allow them to start flying again soon," he said.

He points to the famous 1982 incident of British Airways Flight 9, a Boeing 747 with 263 passengers on board, that lost power to all four of its engines after passing through a volcano ash plume over Indonesia, only to regain power and land safely.

Air regulators closed the airspace over Indonesia for a couple days, but then quickly reopened it, only to have a Singapore Airlines 747 lose power to its engines because of the ash plume 19 days after the British Airways incident.

"Airlines now are really pushing the authorities, just like they were then," he said.

So when will it be safe enough for him?

"When the magma stops interacting with the water, the plume will drop to below a few kilometers and it will then be just a local problem, not affecting the rest of the world. But exactly when it might do that is anybody's guess," he said.

"Volcanology, unfortunately is a more inexact science than weather forecasting," he said.

Looking for more from the Post-Gazette? Join PG+, our members-only web site. You'll get exclusive sports content, opinion, financial information, discounts from retailers and restaurants, and more. Our introduction to PG+ gives you all the details.