An investigation of changes to commercial aircraft flight paths during volcanic eruptions

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 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 the paths of aircraft around erupting volcanoes and when VAAs have been issued, and the impact these routes have on flight schedules and diverted aircraft’s fuel consumption, have not been closely examined. Here, we investigate the behaviour of commercial aircraft during times of volcanic ash emissions as reported in VAAs. We use publicly available flight trajectory data during several ash-rich eruptions at Etna, Sakurajima, Marapi, Sheveluch, Klyuchevskoy and Ubinas volcanoes in 2022 and 2023. We examine a range of geographic locations and eruption sizes. Flight trajectories during periods when VAAs were issued are compared with flight trajectories during periods when no VAAs were issued. We find that the aircraft largely avoided the air space shown to be affected by ash by VAAs, indicating that they adopt a range of strategies to avoid 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 airspace affected by volcanic ash the greater the deviation of aircraft from their usual 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 help to characterise ash-related aircraft disruption over time. Air traffic is likely to grow in the coming years and VAAC advisory strategies will also evolve so understanding how such changes affect disruption trends may be useful. © The Author(s) 2025.