Volcanic exercises are useful where frequent eruptions of volcanoes do not occur or when (major) system changes have been implemented. Both on-going event reviews and VOLCEX reviews should be conducted at least every three years. A complete (system wide) exercise for volcanic contamination is an extremely complex undertaking as such an event involves a great number and variety of stakeholders. Naturally an exercise is a simulation of a real event and the need to keep the air transport network functioning normally limits the accuracy of the exercise, nevertheless they remain a useful planning tool.
