Nine Volcanic Ash Advisory Centres around the world are responsible for advising international aviation of the location and movement of clouds of volcanic ash.
The Volcanic Ash Advisory Centres are part of an international system set up by the International Civil Aviation Organization (ICAO) called the International Airways Volcano Watch (IAVW).
The IAVW comprises observations of volcanic ash from volcano observatories and other organisations, satellites and aircraft in flight, the issue of warnings in the form of NOTAM and SIGMET messages and, since the mid 1990s, the issue of volcanic ash advisory messages from the Volcanic Ash Advisory Centres identifying areas of volcanic ash and their predicted movement.