Active for millennia , Mount Redoubt has erupted four times since it was first observed : in 1902 , 1966 , 1989 and 2009 , with two questionable eruptions in 1881 and 1933 . The eruption in 1989 spewed volcanic ash to a height of 45,000 ft ( 14,000 m ) . It caught KLM Flight 867 , a Boeing 747 aircraft , in its plume . After the plane descended 13,000 feet , the pilots restarted the engines and landed the plane 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 . As of August 2015 , the Alaska Volcano Observatory has rated Redoubt as Aviation Alert Level Green and Volcano Alert Level Normal
KLM Flight 867
KLM Flight 867
Mount Redoubt