Thomas Colbert, his wife Dawna and their team of searchers have dug up what they say is "potential evidence" that could lead to the true identity of famed 1970s hijacker D.B. Cooper.

Thomas Colbert, a longtime Cooper theorist and investigator, told Fox News the discovery "appears to be a decades-old parachute strap" and was found "right where a credible source claimed the chute and remaining money are buried."

On November 24, 1971, a man calling himself Dan Cooper hijacked a plane flying from Portland to Seattle. He forced the authorities to turn over $200,000 and, wearing a business suit, leapt from the plane somewhere over southwest Washington. He was never seen again. The hijacker has become a cultural phenomenon in the years since, the subject of books, songs, a 2011 convention of "Cooperites" held in Portland, and even an inventive theory about the TV series "Mad Men."

The recently discovered parachute strap.

The FBI pursued clues for more than four decades before finally announcing last year that it was abandoning the effort, having "exhaustively reviewed all credible leads."

Now maybe the FBI will reopen the case. The Colberts said they plan to let the bureau know the location of their dig site and other relevant information that led them to their latest discovery.

The Colberts believe a former army man named Robert Rackstraw might be D.B. Cooper. Rackstraw, a decorated Vietnam War veteran who's now in his 70s and lives in San Diego, was an FBI suspect in the 1970s. In 1979, a TV reporter asked him whether he was D.B. Cooper. Rackstraw's answer: "Could have been." He also said, with a sly smile: "I'm afraid of heights."

Despite his playful initial responses, Rackstraw has insisted for years he is not the hijacker.

-- Douglas Perry