The show was about two investigative reporters who had put together a team to investigate the case. They ended up focusing on a Robert Rackshaw and claimed they had 93 pieces of evidence. He's still alive and was a suspect at one time. What the History Channel did was hire a former FBI Asst. Director and a crime journalist to look into the case and see if the two reporters had a case to take to the FBI.
Long story short the FBI wasn't interested having spoken to one of the reporters a few years ago. Basically said unless people have the money or a parachute the FBI is not interested.
The History Channel did get the flight attendant Tina Mucklow who spent most of the time with Cooper. She hadn't spoken to anyone in 45 years. They also had one of the pilots on also.
Very well done IMO. My opinion is the guy named McCoy was a strong suspect because he actually pulled the same crime off, but was caught. He was killed by the FBI in 1974. They talk to the former agent. McCoy used similar language when he did his hijacking that was not known by anyone at the time. He got $500,000.