Why Aviation Industry Has Cloudy Knowledge Of Risks From Volcanic Ash

From The Guardian:

Tests for higher-risk flying conditions may have helped in current crisis but manufacturers said no.

That a cloud of volcanic ash can bring European flights to a standstill has raised serious questions over the aviation industry's efforts to understand the risks of flying in such conditions.

Rules laid down by the International Civil Aviation Organisation prohibit flights through any amount of volcanic ash, but aircraft and engine manufacturers have never fully investigated the effects of flying in ash clouds. What information they have has been gleaned from inspecting planes after they have flown into ash plumes by accident.

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