We're beginning to chase our tail on the question
Is It Safe to Fly and we need limits from the engine manuafactures.
Many of the demands arise from folks with little experience in managing aviation safety but never-the-less consider themselves experts in knowing when it's safe enough.
In trying to keep it simple, the industry has arrived at today's safety record based on lots of experience including data both analytical, emperical and test based. This is embodied in the regulations including the one most at play here Continued Airworthiness.
Under Continued Airworthiness lots of emperical assessments are offered based on a smattering of test data, real experiences and analysis. Turn the crank and you develop a rational for continued flying with intelligent monitoring as controls are implemented. This is the provence of the OEMs and Operators and has to meet the approval of the regulators to ensure that things do not get out of hand.
Just because the observer of aviation does not see the details or understand the process doesn't mean that it is unsafe to fly. If you really want to audit the process then you have to be as close to it as the regulators.
And by-the-way, such a process of managing safety does not mean that one would expect no incidents of Volcanic ash damage nor symptoms, but it does expect that no harm will come to the passengers.
Fly safe
