UFOs Are Real (1979)
One of many 1970s UFO documentaries, this one features lots of still photos of alleged UFO's, some UFO motion picture footage, and stock footage and images acquired from government and military sources. Among the many people interviewed are UFO researchers Stanton Friedman and Ted Phillips, UFO abductees Betty Hill and Travis Walton, optical physicist Bruce Maccabee, and retired U.S. military officers Jesse Marcel and Wendelle Stevens. The documentary supports the view that alien visitors regularly come to Earth and have perhaps done so for centuries.
One of the best documentaries on this topic.
I personally have to say that the older the documentary the more accurate it seems, because the facts at the time were not contaminated with today UFO hoaxes, sensationalism or otherwise debunking "pollution". It must really be taken at face value in order to really understand, so try to transport your mindset to that time.