There are a number of active volcanoes right now over the world, yet it looks like there are no flying restrictions in Ecuador and Colombia, other than the advisory of avoiding immediate vicinity of the volcanoes.
Current Volcanic Ash Advisories - Washington VAAC - Satellite Services Division / Office of Satellite Data Processing and Distribution
From these reports, it's clear that satellites can do a good job on detecting ash concentration. Why are they resorting to computer simulations then?