European transport ministers have agreed to set safety limits for flying through volcanic ash. They've also decided to unite the national airspace of the EU's 27 members into just nine blocks by June, 2012.

The move could help coordinate air traffic during future crises. The ministers had 'serious concerns' of granting financial aid to airlines grounded by such crises.

Meanwhile, flights in Britain and Ireland returned to normal after 150 cancellations. However, Europe's Brussels-based aviation coordination centre, Eurocontrol, has warned of possible further airport closures Wednesday, most likely in Britain.

Brian Flynn, Eurocontrol, Deputy Head of Operations, said, "There's some risk that tomorrow morning there may be some limited closures in the northwest of the United Kingdom. We are not expecting that will be significant and at the moment there is no indication that there'll be anything like a return of the levels of potential ash coverage which happened over the last week."