I'm still amazed at the IMO totally unbalanced view so many are taking about this whole thing. I also accept that I am heavily leaning in a particular direction too and am at risk of being blind to the inaccuracies of my own logic. But, I have heard it stated more than a few times that previous ash encounters have not resulted in a single accident and even the ones that included engine flamouts, had engines sucessfully restarted and a safe landing completed.
Imagine a design fault which had caused over reported 100 incidents (and likely many more unreported) leading to damage and a combined total of hundreds of millions of dollars in reapir bills. One year alone had 23 incidents. 7 incidents involved engine failure including two with all engine loss but none resulted in accidents. The occurence of the issue could be loosely forecast but it was difficult to narrow down the exact conditions under which it would occur. The fact that 100 issues had occured at all suggests that inadvertent and unexpected recurrence was both possible and likely. Are you really telling me that the public and the industry would accept an amendment to the regulations to allow continued flight of affected aircraft as long as they don't enter flight conditions which were already known to guarantee the problem would arise? And all because the industry itself was compaining that they would lose money and risk collapse if they were not allowed fly?
Of course not. The authorities would be firm and insist that the manufacturer(s) involved do something about it immediately, and would only allow flight if they were sastified, using hard proof from tests and unquestionable technical confirmation that the issue had been resolved or at least could be guaranteed to not recur under all but the most rare and easily avoidable conditions.
Now, of course, that's a stupid comparison, but really if you think about it, it is effectively what this ash thing is about. Safe airspace was designated using a best guess method. Many aircraft, including some civilian machines continued (some yet to be confirmed) to have issues. Does that not say the best guess wasn't good enough? Nope. Cause it'd be too painful and difficult to say "Whoops. Got it wrong. Let's try again." And as always seems to happen, the problem quickly goes away by itself, nobody was hurt, no aircraft fell out of the sky (if I hear another pilot say "what's the problem? I don't see aircraft falling out the sky" I'll punch him.) and it can all be quietly put to bed, even though all the evidence suggests it didn't quite go as smoothly as was originally hoped.
I tell ya, sometimes this industry and the people in it make me dizzy, with all their declarations that they can not be shaken from accepting the lessons of the past and that commercial pressure shall never be allowed influence judgement when it comes to issues that can cause damage or affect safety regardless of the cost. But of course, that only applies when it suits them. A la carte professionalism I suppose you'd call it.