In article
,
writes:

In the hundred something years that airplanes have been flying, not a year
has gone by without volcanoes erupting somewhere on the planet. There have
been a couple of anecdotal run-ins at very high altitude - certainly worth
practicing some avoidance, but the death toll still remains at zero. The
European governments must feel a great sense of injustice at being
criticized for pulling the main circuit breaker on the entire society in
their latest _prevention_ efforts, causing untold damage and hardship for
millions for no justifiable cause.

Safety is a pretty justifiable cause. Nobody dies from accidents until the
accidents occur. The fact that nobody has died from a particular type of
accident does not mean that no precautions to prevent it should be taken.

Flights encountering volcanic ash have been few in number thus far, and
they've all been lucky. Assuming that aircraft flying over the ocean will
always be able to glide to land after an ash encounter is irresponsible.

The current known safe threshold for ash in jet engines is zero.