Why does this preclude QF flights operating ML-SY at say FL200, day operations only to remain visually clear of ash cloud?
I am aware of two recent occurrences on the NZ south island where light aircraft flew into ash in areas that were not reported on Sigmets. In both cases there was a noticeable build up ash on the aircraft. In both cases it was around 12,000ft. The ash was described as 'sparkling' by observers after landing. The pilots reported that it was not visible in the air, and only noticed a build up on the aircraft.
I guess everyone can make their own calls. But I could fully understand an airline not wanting that in their new engines.