Active for millennia, Mount Redoubt has erupted five times since 1900: in 1902, 1922, 1966, 1989 and 2009. The eruption in 1989 spewed volcanic ash to a height of 45,000 ft (14,000 m) and caught KLM Flight 867, a Boeing 747 aircraft, in its plume (the flight landed safely at Anchorage). The ash blanketed an area of about 7,700 sq mi (20,000 km2). The 1989 eruption is also notable for being the first ever volcanic eruption to be successfully predicted by the method of long-period seismic events developed by Swiss/American volcanologist Bernard Chouet. The Alaska Volcano Observatory currently rates Redoubt as Aviation Alert Level Green and Volcano Alert Level Advisory.
