A group of amateur sleuths may be close to figuring out who D.B. Cooper really was.

If you don't know, he's the man behind the only unsolved airline hijacking case in United States history. On Nov. 24, 1971, a man who called himself Dan Cooper hijacked a Northwest Orient Flight from Oregon to Washington.

He demanded $200,000 and four parachutes, and he got it when the plane landed in Seattle. Then the plane took off again for Mexico City. Somewhere between Seattle and Reno, Cooper jumped from the plane with the ransom money.

His fate has remained a mystery until this day, and no one has been able to identify the man who became to known as D.B. Cooper. Even the FBI hasn't been able to figure it out, saying last summer it had “exhaustively reviewed all credible leads."

But now Citizen Sleuths – a group that's been working to crack the case – may have found new evidence on the clip-on tie Cooper left behind on the flight.

Citizen Sleuths analyzed particles from the tie, finding cerium, strontium sulfide, pure titanium and other elements. They're all rare elements that are used for very specific things – like in Boeing's high-tech Supersonic Transport Plane, which was being developed with government funding in the 1960s and 1970s, Tom Kaye, the lead researcher of the group, told King 5.

Based on the elements found on the tie, King thinks Cooper could have been an engineer or a manager in one of Boeing's plant.

But the group wants help from the public – especially those with experience in aerospace engineer around that time – who may know more about the particles and what they could have been used for, with Kaye telling King 5: “Someone may be able to look at those particles and say ‘Oh my gosh. I know what that means having those particles on the tie."

For more information on the particles Citizen Sleuth has identified and how to contact them, click here.

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