The VAACs are part of an international system set up by the International Civil Aviation Organization (ICAO) called the International Airways Volcano Watch (IAVW).

The London VAAC is responsible for monitoring and forecasting the movement of volcanic ash over the United Kingdom, Iceland and the north-eastern part of the North Atlantic Ocean.

Although this is a relatively small area, it covers some of the busiest airways in the world. A volcanic eruption on Iceland can quickly affect a large area of airspace, as strong winds spread the ash downwind from the volcano. Air traffic control organisations need to react quickly to the forecasts issued by the VAAC so that aircraft can be diverted onto alternative safe tracks.