Has anyone considdered difference of flying into areas where dust concentrations from land erosion, desert dust etc. (silt, sand and other non organic particles)blown up by wind and thermals vs. flying in areas where possible volcanic ash is present.
Dust by definition is 0.1-60 micron, desert dust and volcanic ash particles being blown over long distances are about the same size. Keep in mind that desert dust is eroded volcanic material by origin, look the same under the microscope and share many other properties. I do not reacall the whole airspace in Europe being closed for buisness when the muck from Sahara or elswhere blows in, as happens occasionally each year.
As for the ash from Iceland, it might have been localized over small portions of Europe in consentrations considdered unsafe for turbine powered aircraft, but for most of the European airspace particle concentration was by far less than seen during dust storms blowing in from Africa.
Enough said, as has been mentioned in this thread before, to eliminate all risk from aviation all aircraft should remain grounded and global transport should turn to alternative means.