I remember Walter Cronkite looking the viewers right in the eye, saying that NORAD radar has NEVER tracked any UFOs. Years later we find out that NORAD's radar, at that time, only looked for incoming targets - not those that were flying parallel to the earth's surface. The government [dis]information folks probably forgot to tell him that.
Much like the standard line back then, "There CAN'T be UFOs because nothing shows up on radar."