According to an new study into the Eyjafjallajökull volcano ash cloud. It appears that more volcano ash was up in the air then originally estimated. The estimation now is that the amount of volcano ash was around 100 times more then expected during the eruption. This has serious implications to air travel in the future if there is a repeat of the Eyjafjallajökull volcano eruption scenario. But most of Eyjafjallajökull volcano ash was small and fine volcano ash that did stay long time up in the air.
This is the conclusion in a study that was made by Mark Woodhouse (and more people) and is published in Journal of Geophysical Research. Sadly I do not have access to this study (I am too poor to do so). So I an only repeat what the Rúv News is saying about this study.
News and links
Öskufallið var meira en við héldum (Rúv.is, Icelandic)
Journal of Geophysical Research