In article ,
Neil writes:
Why then is it so important that aircraft avoid what seems to be a
little bit of fine dust?

I understand that the plane can suffer engine failures etc if it goes
through dense cloud of volcanic ash but is that likely to happen at
such limited concentrations?

I think that past experience when aircraft have encountered such clouds
elsewhere in the world indicates that the answer is yes. A jet engine
must have an awful lot of air going through it, so it wouldn't need to
be very concentrated dust for it to start clogging things up after a
bit. I would imagine that any old piston-engined aircraft would be
pretty much unaffected.
--
John Hall
"Acting is merely the art of keeping a large group of people
from coughing."
Sir Ralph Richardson (1902-83)