The FBI reports it has a “credible” lead in the D.B. Cooper case involving the 1971 hijacking of a passenger jet over Washington state and the suspect’s legendary parachute escape.

“This is an old case, it happened at a time when there wasn’t DNA evidence and we weren’t able to solve crimes instantaneously with genetic codes,” said Geoffery Grey.

Grey, who’s spent years researching D.B. Cooper and is set to release the book “Skyjack: The Hunt for D.B. Cooper” next week, joined 97.3 KIRO FM’s Ross & Burbank Show to share some Cooper insider-knowledge and his best guess as to what the FBI’s lead that could break the legendary case.

The hijacker, dubbed “D.B. Cooper,” has remained a mystery in the 40 years since a man jumped from a Northwest Orient Airlines 727 flight with $200,000 in ransom.

The recent tip provided to the FBI came from a law enforcement member who directed investigators to a person who might have helpful information on the suspect, FBI spokeswoman Ayn Sandalo Dietrich told The Seattle Times on Sunday. She called the new information the “most promising lead we have right now,” but cautioned that investigators were not on the verge of breaking the case.

“With any lead, our first step is to assess how credible it is,” Sandalo Dietrich told the Seattle Post Intelligencer on Saturday. “Having this come through another law enforcement (agency), having looked it over when we got it – it seems pretty interesting.”

According to Grey, parting the clues and reading through the lines, it appears the FBI believes Cooper is dead. But that could be said for most Cooper suspects – the hijacking happened 40 years ago, and Cooper’s age is estimated to be almost 90-year-old.

Federal investigators have checked more than 1,000 leads since the suspect bailed out on Nov. 24, 1971, over the Pacific Northwest. The man who jumped gave his name as Dan Cooper and claimed shortly after takeoff in Portland, Ore., that he had a bomb, leading the flight crew to land the plane in Seattle, where passengers were exchanged for parachutes and ransom money.

The flight then took off for Mexico with the suspect and flight crew on board before the man parachuted from the plane.

“D.B. Cooper is the name of the legend,” Grey said. “It was a myth invented on the night of the hijacking itself. The hijacker boarded under the name Dan Cooper, which is actually a promising lead.”

At the time, FBI agents didn’t know the significance of the name Dan Cooper, the name that was printed on the ticket that the hijacker boarded the plane with. “But now, we know that Dan Cooper is the same name of a French comic book character,” a military hero who would jump out of planes.

Many researchers of the Cooper case, Grey said, believe that Cooper was French Canadian. In the note he passed to the stewardess on the plane, he demanded $200,000 in American currency.

“So the request for American currency could suggest that hijacker was French Canadian,” Grey said.

Otherwise, the hijacker would have simply requested $200,000.

Grey in interested in piece of missing evidence. He said he asked the Seattle bureau office where Cooper’s cigarette butts from the plane had gone, but no one in the office knew where they were.

Dietrich said the FBI’s evidence was sent to a lab in Quantico, Va., for forensic testing. She did not provide specifics about the item or the man who provided the evidence’s identity.

But as the FBI creeps closer to an answer, Grey warned of the Cooper curse – “As soon as you’re close to catching him, he manages to get away.”

The Associated Press contributed to this report