Preliminary results from the European exercise to assess revised response procedures to a repetition of the 2010 volcanic crisis indicate they would provide much-improved access to airspace.
Seventy percent of all planned flights would have taken place, says air navigation organisation Eurocontrol, some three times the number that managed to become airborne during last year's eruption of the Icelandic volcano Eyjafjallajökull.
"Real progress has been made since last year in improving operational efficiency while maintaining safety," it says.
But Eurocontrol also admits: "There are still differences in the application of these revised procedures, which require further efforts at European level to harmonise national responses."
Seventy-seven airlines and various regulatory agencies participated in the two-day exercise, which simulated the eruption of another Icelandic volcano, Grimsvötn.
The exercise tested the capabilities of an interactive crisis visualisation tool, Evita. This prototype version enabled the display of ash concentration data from the London Volcanic Ash Advisory Centre on the Central Flow Management Unit's operations map.
It also showed the co-ordinates of hazardous areas - as declared by states via NOTAMs - and detected sectors, airports and flights potentially affected by ash levels.
Eurocontrol says the tool "allowed for improved decision-making and use of airspace by aircraft operators". Final results of the exercise will be detailed in June.
Analysis of ash from the 2010 event shows that the "airport closures were justified", says researcher Susan Stipp, who has co-authored a risk assessment paper on the Eyjafjallajökull particles.
She says there was "no real protocol" to analyse the capability of ash to damage aircraft and that airports "might make decisions based on pressure rather than on scientific fact".
Nanotechnique research, newly published in the Proceedings of the National Academy of Sciences, shows the particles were "extremely fine-grained, extremely sharp and quite hard", with a melting temperature lower than those in jet engines, making them "dangerous" to aircraft. Stipp says the work also resulted in a protocol for assessing the risk of ash "so proper decisions could be made".