DUBLIN (AP) — Iceland's volcanic ash threatened European air space once again Tuesday, forcing Ireland and some North Atlantic islands to temporarily shut down airports for the first time in 12 days.

Eamonn Brennan, chief of the Irish Aviation Authority, warned of "a summer of uncertainty" in the air due to the continuing eruption of Iceland's Eyjafjallajokul (ay-yah-FYAH-lah-yer-kuhl) volcano.

In Brussels, European Union transport ministers held another emergency aviation meeting and emerged vowing that reforming the continent's patchwork air traffic control system into a one seamless airspace was a "top priority." Germany and France also demanded binding rules to determine when airspaces should be closed and planes grounded because of volcanic ash.

Airlines and airports complained bitterly that EU uncertainty during last month's volcanic crisis grounded too many flights for too long last month. In all, more than 100,000 flights were canceled, inconveniencing 10 million travelers.

Aviation authorities shut down airports throughout Ireland, Scotland's Outer Hebrides islands and the Faeroe Islands for several hours Tuesday after unexpectedly strong and unseasonal winds drove a thick cloud of ash southward from Iceland.

Irish air space reopened at 1 p.m. (1200 GMT, 8 a.m. EDT) and services were scheduled to return to normal as the ash drifted south into the open Atlantic at too low an altitude to pose a risk to aircraft.

Britain's National Air Traffic Service said there was no immediate threat of disruption to British airports but said the situation remained "dynamic." Ireland said there might be new shutdowns Wednesday.

Hanging over all official statements were fears that the volcano in southeast Iceland could keep scattering ash — and travel chaos — across Europe all summer.

"We remain at risk (of further shutdowns), particularly towards Wednesday," Brennan said in a telephone interview. "We're probably facing a summer of uncertainty because of this ash cloud."

Brennan said Ireland had no choice but to shut its air space at 7 a.m. (0600GMT) Tuesday because a thick cloud of ash was reaching the island. The ash generally poses a risk only to aircraft at lower altitudes, when they are ascending to cruising altitude or coming in to land.

Brennan said prevailing winds normally would push the ash northward to the Arctic, but turned southward this week, sending ash straight over the Faeroes, down past the Hebrides on Scotland's northwest coast and over Ireland, which lies 900 miles (1,500 kilometers) southeast of Iceland.

Ireland's temporary shutdown grounded more than 200 flights, most of them operated by airlines Ryanair and Aer Lingus. Both airlines scheduled extra flights in the afternoon and evening to clear the backlog of stranded customers.

Iceland's Institute of Earth Sciences said the volcano's plume has risen this week to nearly 5.5 kilometers (18,000 feet) following several large explosions. It said tremors emanating from the volcano have intensified since Sunday night and the eruption that began April 14 shows no signs of ending.

The last time this volcano erupted — in 1821 — the eruption lasted for over a year.

Among the tens of thousands of temporarily inconvenienced passengers was David Cameron, leader of Britain's opposition Conservative Party. He was scheduled to address rallies in Northern Ireland in advance of Thursday's British election — and became one of the first to fly into the British province once air restrictions were lifted.


Associated Press Writers Raf Casert in Brussels, Jan Olsen in Copenhagen, and David Stringer and Raphael Satter in London contributed to this report.