D.B. Cooper Skyjacking Mystery: Man ID'd as the Hijacker in Upcoming Documentary Is a 'Viable Suspect,' Says Retired FBI Agent

Over the past four and a half decades, the so-called D.B. Cooper skyjacking case has captivated countless armchair detectives – not to mention teams of FBI investigators – hoping to finally crack the nation’s only unsolved act of air piracy.

Now a California man, who has assembled a team of investigators, thinks he may have finally solved case, which will be detailed in the two-part History Channel special D.B. Cooper: Case Closed? that airs on Sunday and Monday.

“In my 35 years I’ve never seen as much evidence on any case I’ve worked on,” says Tom Colbert, a former research director for LA’s local CBS affiliate who assembled a team of retired investigators [including a dozen former FBI agents] to re-examine the case for nearly five years. “I’m absolutely certain in my mind that we’ve got him. It’s just a matter of time before he has to admit it.”

The identity of the alleged culprit, who is confronted by Colbert’s investigators at one point during the upcoming docu-drama with cameras rolling, will be revealed during the program.

The man who became known as D.B. Cooper first made headlines in November 1971 after he boarded a commercial flight in Portland and told a stewardess that he had a briefcase filled with dynamite.

The plane was bound for Seattle and by the time it landed the authorities had delivered the $200,000 in cash he requested, along with four parachutes.

He ordered the pilot to fly him to Mexico, but somewhere near the Washington-Oregon border he strapped on a parachute and leaped from the jet into a rainstorm, never to be seen again – although $5,800 of the money was discovered by an 8-year-old boy on the edge of the Columbia River nine years later.

The FBI, who did not respond to PEOPLE’s request for a comment on the case, has long maintained that Cooper probably didn’t survive the risky nighttime jump. Over the years, their case files have grown to more than 60 volumes.

•

“The D.B. Cooper case is a mystery like any case where you don’t get resolution, but there has to be an answer,” Ron Hilley, who spent 24 years as an FBI agent and served as a member of the investigative team that re-examined the case, tells PEOPLE.

“He [the man they name as the culprit] looks like an extremely viable suspect to me. I would love to see the explanation that clears him.”

D.B. Cooper: Case Closed? airs on Sunday and Monday on the History Channel