Pressure grew today for new, clear rules to decide on closing airspace because of volcanic ash as European transport ministers held another emergency aviation meeting.

Germany and France demanded binding rules covering when planes can be allowed to fly.

Last month's chaotic closures of much of Europe's airspace showed the need to reform the continent's patchwork air traffic control system.

Airlines claim a political overreaction kept far too many flights grounded - 100,000 in all - over ash from Iceland's erupting Eyjafjallajokull volcano.

The ministers were seeking more co-ordination over airspaces to avoid airline chaos and commercial losses because of events like the volcanic ash crisis.

"It's simply not acceptable that every country just does what it wants. We need consistent rules," said German Transport Minister Peter Ramsauer.

French Transport Minister Dominique Bussereau called for "an efficient and fast system for managing such a crisis."

The European Aviation Safety Agency needs to develop a real expertise enabling it to better calculate ash levels and determine how much aircraft motors can cope with, he said.

Underscoring the urgency, Spanish Transport Minister Jose Blanco had maps of today's volcanic ash cloud spreading over Ireland and Scotland before the meeting opened.

Mr Blanco acknowledged that "there must be more co-ordination to be more efficient."

EU Transport Commissioner Siim Kallas is asking the EU's member nations to give airlines relief such as market-rate loans and deferring payments for air traffic control services.

Much of the problem is that the EU's airspace is still cut up in 27 different zones. Mr Kallas is pushing for an "open sky" system where traffic could flow more seamlessly and wants to get a European network manager in place this year.

Europe's air traffic control agency Eurocontrol - which groups 38 member states - also has been pushing for implementation of the Single European Sky concept, which has been under negotiation for two decades.