The first official military case file on UFO sightings began in 1948 after a large number of credible witnesses claimed to have seen alien space crafts. Learn what the file said in this clip from Season 12, Episode 1, "The Alien Hunters". #AncientAliens Subscribe for more from Ancient Aliens and other great HISTORY shows: http://po.st/SubscribeToHistory Find out more about the show and watch full episodes on our site: http://po.st/AncientAliens Check out exclusive HISTORY content: History Newsletter: http://po.st/HistoryNewsletter Website - http://po.st/HistoryWeb Facebook - http://po.st/HistoryFacebook Twitter - http://po.st/HistoryTwitter "Ancient Aliens" explores the controversial theory that extraterrestrials have visited Earth for millions of years. HISTORY®, now reaching more than 98 million homes, is the leading destination for award-winning original series and specials that connect viewers with history in an informative, immersive, and entertaining manner across all platforms. The network's all-original programming slate features a roster of hit series, epic miniseries, and scripted event programming. Visit us at http://www.HISTORY.com for more info.