Not to sound patronizing, but this sounds a bit superficial, Q.G.
As a person working in the aviation sector, I can tell you that things aren't black and white like that. The aviation business in general lives with far more stretched economic balance than other industries. Expenses are ENORMOUS. I'm not even saying that a 4 days stop will put everyone out of business, but things aren't simple as you try to state them.
Well, yes they are.
Sure expenses are enormous. So is income. The simple sum, setting days without income against days with, is completely accurate. As is pointing out that a day not flown does not equal a day's income completely lost. People will have to go places, if not today, than tomorrow. All those thousands stranded at Schiphol, for instance, are still waiting to fly to their destination. And your airline isn't going to fly them there for free. Most people who hadn't commenced their journey will be doing so as soon as they can again. So it's not a complete loss, but largely a postponed income.
Not to mention the fact that only a tiny (though busy) air space is closed. KLM, for instance, though no longer flying in north west Europe for a couple of days, is still happily flying elsewhere over the world.
The loss, or postponed income, most airlines now experience is only part of their business.
So my 0.8% was a gross exageration. It's actually far less.
And ash doesn't move in "blocks". There might be "an awfull lot of air in which there is not", but even a tiny bit might turn into glass and occlude the combustion chambers. Do you know how narrow are those ducts? So, maybe you can run 20 times into a volcanic ash cloud without running into serious trouble, but it takes one time to have all the blame on you, without excuses. That's why I also think that those test flights are a bit of a "commercial" boutade. Without specific instrumentation, what are you exactly testing? Is that like "OK, if we don't lose both engines, then flying here is ok?". Sorry, it doesn't work that way
Yes, that sounds like a grave situation.
But dirt is in the air constantly, in large part thanks to the planes themselves
, and that dirt will do what it does with or without a volcano doing its business somewhere. Checks, maintenance, and all that, have to be performed anyway.
So the question is how much of an extra burden the ash this volcano spread out over Europe would be.
And the thing is that the amount of ash in the air space is neglible in lots of it. Not present in most of it.
It may, for instance, be confined to a layer, with layers below it completely free of it. And if you can't fly at 10K, but can at 5K, you just fly at 5K.
It may also be so dillute that it isn't detectable as an ellevation in pollution levels at all. In which case there is no ellevated risk either.
Well, sorry for the digression, it's just for the pleasure of discussion!
And P.S.: there is no such thing as planes leaving "dirt trails"
Worthless to mention that the rumours running some time ago about planes using some weird chemical compound to deliberately leave trails was something which should carry the authors in front of a jury, in my opinion. But every psycho has the right to speak up, nowadays, and is usually given more credit than those competent..
You perhaps should get out more if you think that dirts trails are but a rumour.
I live underneath an airtraffic lane, and the air above our heads is criss crossed by brownish exhaust trails. On nice, calm summer days, with no wind, the air slowly fills with the dirt you haven't heard about even though working in the industry.