Albert M. Chop (originally, so it seems, Mathew Albert Chop, according to Richard Hall and obituary information that emerged after Mr. Chop's death) started out as a confirmed skeptic when first exposed to UFO cases in his government position. However, over time the evidence "crystalized" (the word used in "U.F.O." narration) until he could only conclude that UFOs were real with intelligence behind their identity.
UFO incidents alone weren't the impetus for his change of mind. He also met military people and members of the scientific community on a regular basis who influenced his thinking significantly. In this scene from the movie, based upon a true event, a highly skeptical Chop (Tom Towers) is asked by a top scientist what is new regarding "flying saucers." When Chop dismisses the question, he is advised, if not chided, by the scientist (portrayed by William Solomon) that we must keep our minds open to all possibilities.