VAACs are responsible for advising aviation of the location and movement of volcanic ash clouds.
There are 9 VAACs covering the world as part of the International Airways Volcano Watch (IAVW) established by International Civil Aviation Organisation (ICAO). Each of the nine centres under the IAVW responds to reports of volcanic ash within their region and provides forecasts to the aviation community of ash cloud extent and movement. Observations may come from ground stations and volcano observatories, aircraft in flight or orbiting satellites. The ash warnings issued are in the form of Volcanic Ash Advisories and SIGMETs describing the current and future extent of ash.