Boeing tells you not to fly into volcanic ash clouds. Eurocontrol and several member nations published a clear policy that prohibited IFR flight into areas they deemed unsafe due to the volcanic ash cloud. They assessed the risk and decided it was too high for continued IFR flight. That is the basis of sound risk management when it comes to aviation safety.
That assetertion is disingenuous.
The issue was not flight into volcanic ash cloud, the issue was flight in an airspace that could have had VA particlates.
There will always be second-guessers. The fact that there were no ash incidents gives clear evidence that the Eurocontrol policy was successful.
argumentum ad ignorantiam.
There is no way to tell how many incidents or mishaps there would have been without the policy
So no burden of proof. Ergo, argumentum ad ignorantiam.
Airlines now want the governments to pay them for the money they think they lost. What would have been the cost of even ONE crash due to ash injestion? I think the airlines may have saved money...
The airlines were financially damaged do to mis-management of a situation, as such yes they should be. They were damaged by the actions of another party out of their control, as such, they have scope for recompense of damages.