Updated at 8:50 a.m. Eastern.
Iceland's volcanic ash renewed its threat to European air space on Tuesday, forcing Ireland to shut services temporarily for the first time in 12 days - and reminding European leaders they still must improve their aviation coordination system.
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 the night before.
Services were scheduled to return to normal Tuesday afternoon as the ash kept moving south into the open Atlantic at too low an altitude to pose a risk to aircraft.
But the shutdowns provided an alarming backdrop for European Union transport chiefs meeting in emergency session in Brussels.
They still are seeking stronger systems to manage the fallout from weeks of ash emissions from Eyjafjallajokul - amid fears that the volcano in southeast Iceland could keep scattering ash across Europe all summer.
In Brussels, European Union transport ministers held an emergency meeting Tuesday to seek better coordination within the continent's patchwork of nationally controlled airspaces. Germany and France demanded binding EU-wide policies on ash levels that would allow planes to fly and determine when airports should be closed down and reopened across the 27-nation bloc.
Airlines and airports complained bitterly that EU uncertainty during last month's crisis meant too many flights were grounded for too long last month. In all, more than 100,000 flights were canceled, inconveniencing 10 million travelers.
Eamonn Brennan, chief executive of the Irish Aviation Authority, said Ireland had no choice but to shut its air space at 7 a.m. (0200GMT) 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 about 900 miles southeast of Iceland.
All the affected nations and regions planned to reopen services in the afternoon as the ash traveled south into the open sea.
"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."
Ireland's temporary shutdown grounded more than 200 flights, most of them operated by airlines Ryanair and Aer Lingus.
Iceland's Institute of Earth Sciences said the volcano's plume has risen this week to nearly 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.
Among the tens of thousands of inconvenienced fliers was David Cameron, leader of Britain's opposition Conservative Party, who delayed plans to fly into Northern Ireland to seek support there before Thursday's British election. Cameron said he would fly to the British province later Tuesday once its airspace reopened.
"We are battling through everything to make this happen," he said.