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On 30 April, a pilot report of a "plume to 20,000 ft over Iliamna Volcano" gave rise to a snowballing reaction within the aviation community. The nonevent culminated in the issuance of an AVO Information Release stating that no eruptive activity was occurring at any Cook Inlet Volcano and that sightings of intense steam clouds in combination with spring weather systems were common at this time of year.
AVO Anchorage received a message on the recorder from the Weather Desk at Anchorage Center (FAA) inquiring about activity at Iliamna. A return call at 1000 yeilded the information that a PIREP of a "20,000-ft plume" had prompted issuance of an air traffic advisory and that flights were being rerouted to well above and around Iliamna. AVO Anchorage quickly verified no change in seismicity and reported this information to the FAA. A subsequent report of a plume over Redoubt necessitated a similar callback.
By later that afternoon, erroneous word of a possible eruption had spread to the Air National Guard, some airlines, and Kenai Emergency Services. Calls from the Drift River Oil Terminal and the Anchorage Airport Tower prompted AVO Anchorage to again check seismicity and the slow-scan TV display - a clear view of both volcanoes showed typical quiescent steam plumes rising at most 300m (1000 ft) above the volcanoes. Transient weather clouds added altitude to the cloudforms which, we expect, were misinterpreted by pilots.
Around 1630, AVO Anchorage received a flurry of calls from several TV stations, Federal Express, and Elmendorf personnel about the "eruption of Iliamna and the ash cloud heading for Anchorage". Someone at Elmendorf reported hearing this news on TV and said that base personnel were making plans to get children and aircraft indoors. After explaining the situation to critical contacts over the phone, AVO decided to issue a written statement emphasizing the no eruption had occurred.