I think it was the Travel Channel, had an entire program on law enforcement encounters.
The most dramatic was where 5 police agencies followed a UFO as it passed through their jurisdictions. They were in contact with the nearby air force base that denied seeing anything on their radar. Kind of like the movie Airplane where the guy unplugged the radar.
History Channel, especially (daily), and Travel Channel have been running documentaries for years on the subject. You would have to be like the Three Monkeys not to a different opinion after watching.
Oh, I’ve seen the one about the 5 police agencies following a UFO and it is convincing that they saw something. They even described it fairly consistently.