The International Air Transport Association (IATA) has asked European governments to re-think measures that have been adopted during the Icelandic volcano eruption, which has forced the cancellation of several flights.
IATA's director general and CEO Giovanni Bisignani said governments must place greater urgency, and focus on how and when Europe's skies can be safely reopened.
"This means decisions based on risk management, facts and utilising operational procedures that maintain safety," Bisignani said.
Bisignani has called for a meeting with the International Civil Aviation Organization (ICAO) to discuss the responsibility of European governments when it comes to opening or closing airspace in a coordinated and effective manner, based on real data and special operating procedures.
The meeting will also look at how airlines can conduct successful test flights in several European countries to assist governments in assessing risk.
The airlines are also adopting operational measures, including day flights, restrictions to specific flight corridors, special climb and descent procedures and boroscopic engine inspections to detect damage and maintain safe operations.
The IATA has criticised the government's unique methodology for closing airspace based on the theoretical modelling of the ash cloud.
According to news agencies, some smaller airports have reopened and European authorities expect 50% of flights could return to service if the skies are clear.
Authorities in Britain, France, Germany and the Netherlands said their air space will remain closed.
Austrian authorities reopened the nation's airspace with many flights remaining cancelled, and Finland opened its Tampere and Turku airports but shut Helsinki airport. Norwegian airspace reopened on the evening of April 18.