If you want to attempt to forecast where ash is, then your industry can pay for it
Part of the purpose of my last post was to highlight that the industry has done nothing except react 'passively'. Whether this reaction was adequate or technically sound is debatable. Anyway, we have some breathing space while the volcano(es) go(es) quiet and we await the next eruption - expert opinion suggests there will be one, possibly soon.
So what about ash detection? Seems that the only really effective method is to fly an aircraft along a track where VA might be and use lidar and / or sampling to check what's there.
Cost? Really doesn't matter! NOT doing this results in potentially unnecessary shutdowns of airspace, airports and sometimes the whole of UK air transport, with calculable cost x per hour or day. So long as the cost of an accurate forecasting / alerting system is less than a fraction of x, it's worth doing. (fraction calculated from the probabilities of future eruption(s) and of false VA alarms.)
Risk? You can't ask people to deliberately fly research aircraft into high risk areas when there is no accurate VA data.
However, there is a suitable platform for doing just this, at negligible risk to people. Predators with all sorts of fancy sensors (and Hellfires!) are already flying reliably in various places. Why not rip out as much of the expensive bits as possible from some Predators (or another suitable UAV), plus whatever classified bits have to go, mount instead some suitable LIDAR, SO2 sensor and whatever other sensors and samplers would be useful, plus civil transponders, and use them as a picket line somewhere off NW Scotland / Ireland? Flying orbits using (say) 4 aircraft round the clock at various heights in an otherwise-vacant bit of airspace would yield very accurate data on what was heading towards UK. If all else failed, monitoring the in- and post-flight engine condition of the engines would also provide good data.
Why not? - We'd only need to fly the picket line as such when we knew that an eruption was happening. We know where the risk will be coming from. Rest of the time, the UAVs could be used for (military) training in the use of the UAV platform and occasionally checking that the system worked with a quick trip close to a volcano.
OK - would not prevent disruption altogether but would minimise it. And much better than doing nothing proactive!