Italian Reinhold Messner, one of the world's foremost mountaineers, said he watched a UFO "the size of a full moon" for nearly three hours while climbing in the Himalayas. On his return to Katmandu after an unsuccessful attempt on 24,248-foot Mount Chamlang, he said he spotted the UFO as it drifted south into Nepal from Tibet over the mighty snowcapped mountains.

 

Source: http://www.ufoevidence.org/cases/case942.htm