JF
You're so correct. The key word though, is 'could'.
We need to know if it 'will' cause the damage, or not.
At least this period of flying in low concentrations of ash will likely provide an answer.
Granted, with a little forethought, the answer to the 'how much is too much' question could easily (if at a cost) have been discovered.
We will now find out.
The cost to the airlines of the enforced stoppage must exceed by many times what the 'research', which was too dear to do, would have cost.
plus ca change.
We make money (BA forecast £600m loss this year) or we fold.