Thanks for your sensible response.
What is the acceptable amount of volcanic particulate matter that an aircraft can fly through?
I accept that there is a difference between day-flight and night-flight on this subject. We all know that radar isn't relevant.
My point is that it seems like the air is very clear. I appreciate that I can't see further than my window, but I can honestly see 50km, without any apparent airborne particulate matter. The sunset tonight was very normal (I remember when Mount Pinatubo exploded - the sunset was extraordinary). The moon is clear. The stars are twinkling. There is no visible obstruction.
I am genuinely mystified about how there can be such a degree of disturbance when there is no visible airborne particulate cloud. Abrasion damage is a result of time, speed and density of pumice. In the absence of a measurable density of particulate volcanic ash/dust - what is the problem?