It was just about a year ago that the Eyjafjallajokull volcano in Iceland erupted, leading to the widespread disruption of air traffic in Europe. Because of concerns that airborne volcanic ash might damage jet engines, most air routes in and through Europe were shut down for several days. Naturally, airlines and other travel companies were not best pleased, since they stood to lose large amounts of revenue. There was some suggestion that the blanket restrictions on air travel were too sweeping, but there was not much hard evidence presented either way.
The New Scientist site has an article reporting on some new research [abstract], published in the Proceedings of the National Academy of Sciences, that suggests that there actually was cause for considerable concern. (This is not to say that the original decision was based on the kind of evidence presented in the paper.) A group of researchers from the University of Iceland and the University of Copenhagen found that the ash from this eruption was unusually fine, and unusually sharp-edged.
They found that ash released in the first few days of the eruption contained unusually high levels of particles smaller than 300 micrometres across. These particles are most likely to become trapped in jet engines and melt, causing the engines to stall. The particles were also hard and sharp, making them more likely to sandblast aircraft windows, obscuring pilots’ view.
Perhaps the most useful product of the research is a set of testing protocols and methods that can be carried out as an eruption occurs. Using such a methodology would potentially allow regulatory authorities, equipped with a more up-to-date and higher resolution analysis, to tailor flight restrictions so that areas with dangerous amounts of ash could be avoided, while still allowing travel via safer routes.