received more focused attention in recent times due to its increased activity: it erupted in 2001, 2005, three times in 2006, 2007, three times in 2009, and twice in 2010. Of these, the most significant eruption was the 2001 eruption, which produced a high ash plume. This plume dispersed across Alaska, an unusual distance that allowed detailed satellite observations to be made. Nikolski and the surrounding region was the site of several hours of ashfall, represented in satellite imagery as areas of discolored snow. This eruption significantly disrupted air traffic in the area. On June 19, 2012, a pilot reported an ash-producing explosion on Mount Cleveland. Due to continuing seismic activity, the volcano was placed on the USGS Volcano Watch List in the orange or "watch" category the following day. AVO continues to keep Cleveland on the watch because of a persistent anomaly at the summit. AVO suspects it could be dome growth. Other minor ash producing explosions occurred on June 26, July 12, and August 19. On May 4, 2013, the volcano began a low-level eruption, with a plume of ash observed at . The volcano erupted several times in 2014 and 2015, and a single explosion was detected by the AVO on April 16, 2016. In total the volcano has erupted at least 22 times in the last 230 years. Monitoring Today, the Alaska Volcano Observatory monitors activity at Mount Cleveland using satellite imagery. Cloud cover often obscures the volcano, which makes many events difficult to follow. In addition, the low resolution of the satellite imagery allows minor events, which do not make an impression on the satellite picture, to pass unnoticed. There are no seismic or geophysical instruments on the mountain (the nearest are in Nikolski), and some eruptions are first observed by pilots flying over the volcano. A field study was conducted in late 2001, and an automatic system based on thermal anomalies was implemented following eruptive events in 2005. In recent years the Alaska Volcano Observatory has made an effort to expand volcanic coverage westward along the Aleutian Arc. The biggest threat posed by an eruption from Mount Cleveland is its ash plume, which can damage sensitive electronic equipment on overflying planes. Many aircraft traveling over the North Pacific and over the Arctic come within the vicinity of such a plume; the only way to avoid damage is to reroute the flight, which delays arrival