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Volcanic ash is exceptionally hazardous for jet aircraft in flight. Flying through ash can quickly damage the jet engines, causing surging, flame out and immediate thrust loss. Pilots can inadvertently penetrate volcanic ash clouds because airborne weather radar will not reflect off the small ash particles, and the visual appearance of an ash cloud may look very similar to an ordinary meteorological cloud. To aid pilots in avoiding ash cloud areas, the International Airways Volcano Watch (IAVW) agreements have developed under the guidance of the International Civil Aviation Organization (ICAO).


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