The 6 flights put up prove nothing, as they are statistically insignificant.
The daily number of flights over Europe is around 24,000. If the chances of encountering a dense patch of dust sufficient to endanger the aircraft was only 0.01% then nearly 3 aircraft a day would have serious incidents. If it was 0.00% then it would be one aircraft every 4 days.
Try getting the airline insurance company to continue to provide cover if the airlines try and start flying again without scientific approval.
In the meantime, the Airlines are starting to request national and EU compensation in the same manner provided after 9/11.
BBC:
BA seeks compensation for ash chaos