In August 2011, the FBI was investigating a 'credible' tip that someone who had not previously been considered a suspect, and who had died over 10 years ago, was actually the Dan (aka D.B.) Cooper who pulled off the famous plane hi-jacking and ransom in November 1971.
SPOILER: Much of the analysis in the program is based on a factual error, which invalidates two of the main points presented. The narrative presented in the show is based on Earl Cossey's statements that he provided the two back parachutes which were demanded by Cooper. Cossey describes them as being a mix of a common chute, and a highly modified NB-8 parachute. NB-8 stands for "Navy Backpack", and is a chute used by Navy pilots. Cossey states that the fact that Cooper chose the NB-8 chute indicates that he was an amateur who didn't know what he was doing. In addition, much of the later analysis by the experts who were brought in to re-examine the case, was based on the fact that the NB-8 was non-maneuverable, leaving Cooper at the mercy of the winds, which would have either dumped him into the river below the plane, or carried him to a nearby lake, causing him to perish.
The fatal flaw is that Earl Cossey did not provide the two back parachutes which were given to Cooper. Those two parachutes were owned by, and provided by Norman Hayden, a machinist and aerobatic pilot. When Cooper made his demands for two front chutes and two back chutes, Northwest Orient official George Harrison called Pacific Aviation at nearby Boeing Field. He spoke to Barry Halstad, who told him that all they had were seat chutes, not back chutes. He suggested that Harrison call Hayden, a customer of his. They reached Hayden at his machine shop. Hayden was too busy at the shop to deliver the chutes himself, so he put them on a taxi to Northwest. The notes of one of the original FBI agents working on the case do in fact confirm this and list Hayden as the person who provided the parachutes. Both the FBI original notes and Hayden's statements identify the parachutes as Pioneer chutes. This actually refers to the container, not the parachutes inside. The parachutes were identical civilian chutes which were maneuverable and steerable. Therefore, the statements in the program that Cooper showed his lack of experience by choosing an NB-8, were wrong because there was no NB-8. Since there were two identical chutes, there was no choice to be made, and any experienced parachutist would have recognized them as easily used chutes which provide the necessary maneuverability. This maneuverability of course also invalidates the program's statements that Cooper would have been helplessly carried into the water. Northwest paid Hayden for the "rental" of the chutes shortly after the hijacking. The unused chute was returned to Hayden many years later after he went to court to sue for its return.
As for Cossey,, he was a well known expert skydiver and parachute rigger who was contacted by the FBI early in the investigation when they were trying to find out if Cooper was known to the local skydiving community. It was shortly after being brought into the investigation that Cossey began making public claims that he had provided the chutes. He was such a constant figure in press stories that his claims became the common understanding of what had happened, but his claims are not backed up by the documented facts.