Please correct me on this, but didn't BA flight 009 fly into a full volcanic ash cloud at night c180 km from the volcano, as opposed to a clear blue skied day, thousands of miles away from the source?
Also KLM Flight 867, another 747, flew into the plume of the erupting Mount Redoubt, again c180 km from the volcano, causing all four engines to fail.
Is there not some kind of picture emerging there?