A Volcanic Ash Advisory Center (VAAC) is a group of experts responsible for coordinating and disseminating information on atmospheric volcanic ash clouds that may endanger aviation. As at 2019, there are nine Volcanic Ash Advisory Centers located around the world, each one focusing on a particular geographical region. Their analyses are made public in the form of volcanic ash advisories (VAAs), involving expertise analysis of satellite observations, ground and pilot observations and interpretation of ash dispersion models.