Volcanic Ash, Engines and Airframes
Timber, I notice your profile says you have an ATPL. I would have thought that you would understand why Qantas decided to stay put. Any ingestion of volcanic ash will harm not only engines, but also if heavy enough will erode windshield panes, remove paint, clog up air conditioning systems and generally play havoc with the aircraft as a whole. As far as the engines are concerned they do not like having crap left all over the compressors and, worse, the ash turning to glass like deposits on turbines. If Qantas chose to stay on the ground you can be sure they had very good reasons for so doing. I don't know, but I would think that CASA played no role in the decisions made by Qantas despite what was said about "consulting the agency first".