Iceland ash won't ground flights again: ministers

European transportation officialsinsisted Tuesday they have learned from the wide-scale disruption last month caused by ash emanating from an erupting volcano in Iceland and wouldn't let such emissions ground flights again.

The volcano became active again Tuesday after a two-week period of relative calm. That spurred aviation authorities in Ireland, northwest Scotland and the Faeroe Islands in the North Atlanticto shut down services for several hours. Airports in those regions re-opened once the densest ash clouds had passed and movedfarther out overthe Atlantic.

Europeanofficials said they were learning to more accuratelypinpointthe threat posed by such eruptions to avoid having to institute another wholesale, better-safe-than-sorry shutdown like the one that grounded flights for nearly a week in several countries in April.

Airline and airport authorities branded that response overkill; it grounded 100,000 flights and 10 million passengers and cost the industry billions.

European Transport Commissioner Siim Kallas emphasized that, had last month's sweeping safeguards been imposed Tuesday, "a verylarge part" of Europe would have lost its air links again and for days, not hours.

Kallas and transport ministers from the 27-nation European Union agreed Tuesday at an emergency meeting in Brussels to press ahead on plans to unify their divided air-traffic-control networks.

They also committed toresearching new ways of identifying and measuring radar-invisible ash clouds and legally defining safety standards for specific makes of jet engines and the airline industry as a whole.

"We want to give top priority to those measures, which will accelerate the setting up of the single European sky," Kallas said.

Irish airports re-open

Irish airportshave resumednormal operations after they were closed Tuesday morning to avoid a thick cloudof ash from Iceland's still-erupting volcano.

Airports in nine cities, including Dublin, Shannon and Cork, reopened at 1 p.m. local time, the Irish Airport Authority announced.

"Our decision to close earlier today was based solely on the safety risks to crews and passengers as a result of the drift south of the volcanic ash cloud caused by the northeasterly winds," the IAA said on its website.

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

Flights over Ireland from the U.K. and Europe were not affected by the closure.

Iceland's Institute of Earth Sciences said the volcano's plume has risen this week to nearly 5.5 kilometres following several large explosions. It said tremours 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 more than a year