IRISH pilots have claimed that a "vast" area of the country's airspace was not contaminated despite being closed down due to fears over volcanic ash.

The Irish Airline Pilots' Association (IALPA) criticised aviation authorities, saying their handling of the recent flight restrictions due to volcanic ash was a case of "making it up as they go along".

They also complained that the criteria that might have been used to ground airlines has not been published or otherwise made known.

However, the Irish Aviation Authority (IAA) has insisted there was no overreaction.

With flights returning to the skies by last Wednesday, the focus has now shifted to a future reoccurrence of volcanic activity that left hundreds of thousands of people stranded around the world.

IALPA president Evan Cullen said he hoped significant lessons had been learned.

"My difficulty is that they have not published the criteria. In other words, what was the level of the contamination that caused the closure of air space?" he said.

"Our information is that the vast area of Ireland did not have contamination. If they had information on contamination, then why wasn't it published? I suspect they are making it up as they go along and that is not acceptable."

As the crisis calmed down last week, the IAA told an Oireachtas Committee on Transport that closing air space was standard procedure and added: "We are not in the business of taking risks".

An EU agreement reached on Monday to limit future air space closures could reduce the amount of affected services by two thirds.

"If it happens again we have an agreement in place across Europe," an IAA spokesman said.

The three-zone plan will effectively divide airspace into sections varying from a complete flight ban to those where operations can carry on as normal.

"There will be a much smaller area of a no fly zone. The rest of the aircraft will be given routes to avoid areas of contamination," he said.