A Cloud of Volcanic Ash

A cloud of volcanic ash? Please let me know the composition of the ash particles, their size and density of distribution at different altitudes. Then I can draw upon my knowledge of how the density and composition of these particles will affect the engines of my jet aircraft, ie how long they can sustain their flight without incurring damage. Then I can plan my route around or through the dust cloud to minimise risk of damage to the aircraft and its passengers.

What's that? You don't know the composition, particle size, density or distribution of the dust particles? Nor do you know how that will affect my aeroplanes flight characteristics? Well then, how do you know how dangerous it is or is not?

Oh, you've just closed the airspace, well in that case we'll all have to stay at home, thank you.