Volcanic ash ejected into the atmosphere by explosive eruptions has known damaging effects on aircraft. Ash particles can abrade forward-facing surfaces, including windscreens, fuselage surfaces, and compressor fan blades. Ash contamination also can lead to failure of critical navigational and operational instruments. Moreover, the melting temperature of the glassy silicate material in an ash cloud is lower than combustion temperatures in modern jet engines; consequently, ash particles sucked into an engine can melt quickly and accumulate as re-solidified deposits in cooler parts, degrading engine performance even to the point of in-flight compressor stall and loss of thrust power.

Encounters of Aircraft with Volcanic Ash Clouds: A Compilation of Known Incidents, 1953-2009 documents 79 damaging ash/aircraft encounters. Twenty-six of those involved significant to very severe aircraft damage, including nine encounters where engine failure occurred during flight. Fortunately in each of the engine-failure cases, at least one engine was able to be restarted or did not fail, and hence there have been no known crashes as a result of volcanic ash ingestion. However, engine damage resulting from ash ingestion can be very costly - in a 4-engine shutdown incident during the 1989 eruption of Redoubt Volcano in Alaska, USA, the aircraft sustained damage costing US$150 million (in 2013 dollars) to repair.