The FBI in Seattle has recruited a band of amateur sleuths to help solve its 45-year-old head-scratcher of America’s most notorious skyjacker – D.B. Cooper.

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The amateur scientists, who call themselves Citizen Sleuths, are asking for the publics’ assistance as they gather new leads that may link Cooper to The Boeing Company as either an employee or a contractor hired by the tech giant in the 1970s.

The Citizen Sleuths analyzed the clip-on tie discovered aboard the hijacked Northwest Orient passenger jet in November 1971.

The JC Penny brand accessory was put under an electron microscope that found elements like cerium, strontium sulfide and pure titanium.

The scientists claim that such elements were very rare around the time of the hijacking, but were used by Boeing on their supersonic plane, which was being developed with government funding.

The scientists are now trying to link Cooper as a man who may have worked with Boeing.

“These particles, through their shape and composition, can tell a story, but they are inherently difficult to work with because they often represent one very, very small piece of the actual evidence," Citizen Sleuths wrote on their website.

"In some aspects of this investigation, multiple lines of evidence pointed to the same answer, and in others, only a single clue was available to shine a light down a dark tunnel. It should be understood up front that the information presented here represents the best deductions of the researchers on what is certainly a very cold case.”

"The tie went with him into these manufacturing environments, for sure, so he was not one of the people running these [manufacturing machines]," Tom Kaye, the group's lead researcher, told King5. "He was either an engineer or a manager in one of the plants."

Kaye and his band of Citizen Sleuths are now calling on anyone with a background or experience with the aerospace industry in the Pacific Northwest to aid in the investigation.

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In November 1971, a man now known as D.B. Cooper climbed aboard Northwest Orient passenger jet, which was manufactured by Boeing and headed to Seattle from Portland, and told the flight attendant that he had a bomb in his suitcase.

He then demanded $200,000 and four parachutes.

The FBI handed over the money and the parachutes to Cooper as the plane landed at Seattle's Sea-Tac Airport. The aircraft then took off again, heading south.

At some point, he made his now-infamous escape by jumping out of the plane. Cooper, who was said to have been wearing a business suit at the time of the hijacking, was never found.

Read: 45 Years After Plane Hijacking, Mysterious Case of D.B. Cooper Is Shut Down With No Credible Leads

A minimal amount of the money that was given to Cooper was recovered, as was his airline ticket, which was issued to a "Dan Cooper."

The FBI closed the case last July after turning up no new leads on Cooper's identity.

The Citizen Sleuths were granted access to the FBI’s files a decade ago and have recently made their discoveries public with the public appeal for assistance.

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