Quite apart from the rigor (or otherwise) of any risk assessment that might have been done, there is a huge (and un-nerving) disparity between activity in UK/Europe, and the US.
I just heard a snatch of audio from a US Senate sub-committee hearing (presumably Transportation). They'd got a rep from GE Aviation on the stand and asked him two or three obvious and relevant questions. Knowing that it would be VERY unwise to BS or slime his way out, he appeared to answer competely and honestly.
1. Is there a problem with ash in engines? Yes, there is. GE plan to keep each engine on-wing for 5 years. Ash ingestion may reduce this time.
2. What happens? In particular, turbine cooling holes get blocked and damage is likely to be cumulative.
3. What about designs and / or materials that would avoid the problem? Aware of nothing in immediate future and maybe nothing long term.
So why are the European 'authorities' so supine and/or incompetent that they seem unable to extract similar short, succinct summaries of problems and maybe potential solutions on demand? The US is well-known as the litigation centre of the world, so that no-one over there dares speak out plainly. Clearly, the Senate and its committee witnesses are major exceptions! Good for them!