The change in policy marks an increased preparedness for ash emergencies, but the awareness of ash risk to planes is still under investigation. Some argue the strategy is creating more chaos than needed.
"At the moment, here in Europe, the ‘no fly' zones are too big and much too cautious," wrote atmospheric scientist Fred Prata of the Norwegian Institute for Air Research in an email to Discovery News. "Helicopters in northern Norway have been grounded because of a plume in the stratosphere that is composed entirely of SO2 [sulfur dioxide] gas."
Following last year's Eyjafjallajökull eruption, EasyJet airlines agreed to test on-board air sensors meant to warn pilots of approaching ash clouds. But the technology, which Prata created, is not yet in place.
In December 2010, the International Civil Aviation Organization (ICAO) identified the low (teal), medium (gray), and high (red) concentration rates used to map plume levels. As part of the end to the Eyjafjallajökull crisis last year, on April 21, 2010, flying through an atmosphere that contained less than 2,000 micrograms of ash per cubic meter of air was deemed safe.