The FBI said 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. Four decades ago, a man calling himself Dan Cooper jumped out the back of Northwest Orient Flight 305 over Washington State with a parachute and $200,000 of ransom money. It is unknown where Cooper landed or if he even survived the jump. The case lives on in infamy and is referred to by the FBI as "one of the greatest unsolved mysteries," according to Pennsylvania's Fox News.

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. 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.

A piece of the suspect's personal property was also given to the FBI and is currently at the FBI forensic lab in Quantico, Va., where it is being checked for fingerprints and DNA. The FBI obtained a partial DNA sample from the black JCPenney clip-on tie Cooper left on the plane before jumping off and while the FBI extracted a DNA sample in 2001, it did not match up with any suspects. That tie, along with the parachute he discarded, his boarding pass with the words "DAN COOPER" written in red ink, and a few deteriorated bills from the ransom money found in 1980 are the only physical pieces of evidence the FBI's Seattle office has.

Cooper 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. "We've run down thousands of leads and considered all sorts of scenarios," the FBI told CNN in 2007. "And amateur sleuths have put forward plenty of their own theories. Yet the case remains unsolved. Would we still like to get our man? Absolutely."

The agency reminded the public that Cooper was no expert skydiver. "We originally thought Cooper was an experienced jumper, perhaps even a paratrooper," said Special Agent Larry Carr in 2007. "We concluded after a few years this was simply not true. No experienced parachutist would have jumped in the pitch-black night, in the rain, with a 200-mile-an-hour wind in his face, wearing loafers and a trench coat. It was simply too risky. He also missed that his reserve chute was only for training and had been sewn shut – something a skilled skydiver would have checked."

Agents also believe Cooper had no help on the ground. If he had had an accomplice, he would have needed to coordinate closely with the flight crew and jump at just the right moment. "But Cooper simply said, 'Fly to Mexico,' and he had no idea where he was when he jumped," authorities said. "There was also no visibility of the ground due to cloud cover at 5,000 feet." Carr said he believed it was unlikely Cooper survived the jump. "Diving into the wilderness without a plan, without the right equipment, in such terrible conditions, he probably never even got his chute open," he said.

Dietrich has refused to name the suspect or even say whether the person of interest is still alive. "Generally, the large majority of subjects we look into now are already deceased based on the timing of this," she said.