Originally Posted by Stranger

Not sure if we can use these as a proper indicator.

Surely it's not like these guys really wanted to go? So a good excuse should be very welcome.

As to whether these clouds are a real danger, I would think that the answer should not be black and white. Includes a good deal of "we don't know. Also a good deal of "they are very bad for the engines."

I would think, for instance, that if the cloud does not go above FL350, flying above should be OK as long as the concentration at lower levels is not too bad and there is an alternate that can take the plane. In an emergency, the engines might get ruined, but it's not like they'll stop working alltogether.

Real issue is more that, between 200 and 340, the cloud covers an area where most airports are.