The volcano in southern Iceland's Eyjafjallajokull glacier sends ash into the air just before sunset Friday. Thick drifts of volcanic ash blanketed parts of rural Iceland Friday as a vast, invisible plume of grit drifted over Europe, emptying the skies of planes and sending thousands in search of other transportation.

LONDON — A lingering volcanic ash plume forced extended no-fly restrictions over much of Europe on Saturday, as Icelandic scientists warned that volcanic activity had increased and showed no sign of abating — a portent of more travel chaos to come.

Scientists say because the volcano is situated below a glacial ice cap, the magma is being cooled quickly, causing explosions and plumes of grit that can be catastrophic to plane engines if prevailing winds are right.

"The activity has been quite vigorous overnight, causing the eruption column to grow," Icelandic geologist Magnus Tumi Gudmundsson told The Associated Press on Saturday. "It's the magma mixing with the water that creates the explosivity. Unfortunately, there doesn't seem to be an end in sight."

An expansive cloud of grit hovered over parts of western Europe on Saturday, triggering extended flight bans that stranded people around the globe. Continued volcanic activity could produce more plumes if the weather patterns stay the same.

The Icelandic Meteorological Office said the amount of ash in the plume grew Saturday and that the vast ash cloud is continuing to travel south and southeast.

Aviation experts say the volcanic plume has caused the worst travel disruption the world has ever seen.

"I've been flying for 40 years but I've never seen anything like this in Europe," said Swedish pilot Axel Alegren, after landing his flight from Kabul, Afghanistan, at Munich Airport; he had been due to land at Frankfurt but was diverted.

Anxious passengers have told stories of missed weddings, graduations, school and holidays because of the plume.

On Saturday, the French prime minister extended the closure of airspace in northern France until Monday morning. British and German airspace is closed until at least 8 p.m. Saturday, and British Airways is canceling all short-haul flights to and from London airports Sunday. The Belgian, French and Swiss governments extended their ban until Saturday evening.

Shoppers were warned Saturday that continued flight bans could spark shortages of imported fresh fruit and vegetables.