Aircraft responses to volcanic ash advisories during volcanic eruptions

Abstract Volcanic eruptions can inject ash into the atmosphere, which is then advected by meteorological winds, potentially affecting large volumes of airspace. Volcanic Ash Advisory Centres (VAACs) issue volcanic ash advisories (VAAs) when an airspace is likely to contain ash above a concentration threshold. Much research has been done to improve operational ash forecasts of volcanic ash location in the atmosphere, but until now behaviour of aircraft around erupting volcanoes and those for which VAAs have been issued, and the impact these responses have on flight schedules and diverted aircraft’s fuel consumption, has not been closely examined. Here, we investigate real-world responses by commercial aircraft to volcanic activity as reported in VAAs, using publicly available flight trajectory data during several ash-rich eruptions in periods of heightened eruptive activity in 2022 and 2023 at Etna, Sakurajima, Marapi, Sheveluch, Klyuchevskoy and Ubinas volcanoes. We examine a range of geographic locations and eruption sizes. Flight trajectories during periods when VAAs were active are compared with flight trajectories during normal, ash-free periods. We find that aircraft adopt a range of strategies to avoid ash, largely avoiding the indicated air space affected by ash. We also find that, in general, by avoiding ash aircraft also avoided volcanic SO2 plumes. Our results confirm that the greater the volume of air affected by volcanic ash the greater the deviation of aircraft from their typical flight paths. Rerouted aircraft may travel significantly further distances to avoid ash, which results in longer air travel time and delays, suggesting greater fuel consumption and carbon emissions. Further long-term systematic studies of the impact of volcanic eruptions on flight routes and timing would be helpful in determining the amount of ash-related aircraft disruption, as air traffic is likely to grow in the coming years, and VAAC advisory strategies also evolve.