Ireland's airspace will reopen at 1 p.m. (1200 GMT) Tuesday because the threat from volcanic ash has faded overnight, but Irish air travelers face a "summer of uncertainty" because of the long-running Iceland eruption, the Irish Aviation Authority said.

The authority temporarily grounded services at all Irish airports at 7 a.m. (0600 GMT) because shifting winds had pushed ash plumes from Iceland south into Irish airspace, pushing the risk of damage to jet engines beyond acceptable levels.

Eamonn Brennan, chief executive of the Irish Aviation Authority, said the prevailing winds would normally go northward but have switched south this week, sending ash over Ireland approximately 900 miles (1,500 kilometers) southwest of Iceland.

"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."

Tuesday's ash worries also forced aviation authorities in Northern Ireland, Scotland's outermost Hebrides islands, and the Danish territory of the Faeroe Islands to ground flights.

Northern Ireland said it would join the Republic of Ireland in reopening services Tuesday afternoon. But the situation remained unclear in the Hebrides and Faeroes, island systems much nearer Iceland in the North Atlantic.

Among the tens of thousands of would-be fliers inconvenienced 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 later he still planned to make it to the British territory Tuesday.

Ireland became the first country outside Iceland to shut down its airspace since the April 14-22 crisis caused by billowing ash clouds from Iceland's erupting Eyjafjallajokull (pronounced ay-yah-FYAH-lah-yer-kuhl) volcano.

European Union authorities took a week during that crisis to draft new safety standards and more precise rules for governing whether aircraft could travel through ash-tainted air.

In Brussels, European Union transport ministers gathered in emergency session Tuesday to seek better coordination within the continent's patchwork airspace to avoid airline chaos and commercial losses from Icelandic volcanoes or other surprise events.

Germany wants binding rules to define ash concentrations and when to keep airports closed. Airlines and airports complained bitterly that EU uncertainty meant too many flights — more than 100,000 — were grounded for too long last month.

Ireland's temporary shutdown Tuesday grounded more than 200 flights chiefly operated by airlines Ryanair and Aer Lingus.