One year after the eruption of Iceland's Eyjafjallajokull volcano, more than 70 airlines took part in a simulation on Wednesday to prepare for another ash cloud closing European airspace.

The exercise simulated the eruption of the Grimsv�tn volcano in Iceland, sending volcanic ash south across the North Atlantic and Europe, said the International Civil Aviation Organization (ICAO), based in Montreal.

It aimed to validate changes and improvements to contingency plans and procedures in case of another eruption.

Ash clouds from the Eyjafjallajokull volcano forced the closure of large parts of European airspace in April 2010.

At its peak in the week after it began, the eruption caused the biggest aerial shutdown in Europe since World War II, affecting more than 100,000 flights and eight million passengers.

The European Commission estimated airline and travel agency losses from the grounding of air traffic at up to 2.5 billion euros (three billion dollars).

"One of the issues is ... how local coordination fits in with international efforts," said Brian Flynn of Eurocontrol.

"Although the executive decision making responsibility will always be under the control of national authorities, it will be important to establish where the dividing line between responsibilities lies."

Fourteen air navigation service providers, 10 national regulatory authorities, the Volcanic Ash Advisory Centre London, the European Commission, and the European Aviation Safety Agency also participated in the exercise.

On the first day of the exercise on Tuesday, states asked Eurocontrol to open, close or restrict their airspace to aircraft according to their national procedures.

On the second day of the exercise, a new harmonised European approach was to be tested. It allows airlines to decide if they will fly in areas contaminated by ash based on safety risk assessments by national aviation authorities.

The results are to be presented in Brussels on June 6 and 7.

The simulation was not expected to impact regular air travel.