I note many aviation authorities continually announcing closures of airports and airspace "until xxxx GMT today," followed inevitably by new announcements as the opening times must be postponed again and again.
Why not just say "closed until further notice"? Because that's the reality. And it looks stupid for authorities to announce specific times only to revise them again, and again, and again. Why the reluctance to say "we don't know"?
In fact, there seems to be a general reluctance to accept the reality. As long as there's ash in the air, you can't fly. The ash might clear tomorrow, or it might be there a year. There is absolutely nothing that can be done about it, so there's no sense stressing over it.
But there is one way to make the best of it, and I see I'm not the only one thinking about it:
Here's an idea. The companies who are losing revenue could establish a pool of engines of various designs they're willing to trash. Stick them on airframes, and fly, carrying sensitive equipment aka NASA DC8. At destination, strip down engines to determine level of deterioration. Repeat as necessary.
I don't know if the airlines or other losing parties here are willing to make this sacrifice, but it certainly would be useful if someone did, because this is a perfect opportunity to gather data on the effects of volcanic ash, which would make it far easier to determine what levels of ash (if any) are acceptable for aviation. But nobody seems to be doing much of anything. There isn't anything else to do, and there's ash right at the doorstep waiting to be measured, so why not at least try to profit from the situation. If crews are willing to volunteer for the work, at least. And they'd actually be risking airframes, not just engines.
Without some experimental flights by some brave researchers, the threshold of acceptable ash levels will always be zero. It might turn out to be zero even after research is done … or it might not.