Explosive volcanic eruptions have the potential to inject gases including sulphur dioxide (SO2) and silicate ash into the upper and lower stratospheres, which not only has climatic implications but also poses a significant hazard for aircraft flying at these altitudes. The effects of volcanic ash on engines and the main airframe are well documented and although the effects of acidic gases on aircraft are less well known, both species have the potential to result in both hazardous and extremely costly damage. The 2009 eruption of Sarychev Peak, Kuril Islands, affected a large number of flights in the busy North Pacific (NOPAC) region. Here we observe the differential transportation of ash and SO2 using the satellite-based sensors Atmospheric Infrared Sounders (AIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS), highlighting both the usefulness and limitations of these sensors and comparing the observed data to the predicted ash dispersion from the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Data are displayed using Google Earth, which allows a visual representation of the two species in relation to aircraft flight paths in the region, thus allowing an assessment of the threat to aviation due to this eruption.