Americans could be close to the truth in one of the most mysterious cases ever to have haunted the country's Federal Bereau of Investigation.

A woman in Oregon has now come forward, after 40 years, claiming infamous hijacker D.B. Cooper was, in fact, her uncle Lynn Doyle Cooper.

She has also forwarded material for fingerprinting.

Police are yet to determine results of the fingerprint analysis but are reportedly eager to close the case.

Earlier this year, a team that includes a paleontologist from Seattle's Burke Museum released new findings this month that particles of pure titanium found in the hijacker's clip-on tie suggest he worked in the chemical industry or at a company that manufactured titanium — a discovery that could narrow the field of possible suspects from millions of people to just hundreds.

Nevertheless, no one's been able to solve the puzzle, or even determine whether Cooper survived his infamous jump.

The jump from 10,000 feet

On November 24, 1971, the night before Thanksgiving, a man described as being in his mid-40s with dark sunglasses and an olive complexion boarded a Northwest Orient Airlines flight from Portland to Seattle-Tacoma International Airport. He bought his $20 ticket under the name 'Dan Cooper', but an early wire-service report misidentified him as 'D.B. Cooper', and the name stuck.

He sat in the back of the plane and handed a note to a flight attendant. She was so busy she didn't read it until after takeoff: "Miss, I have a bomb and would like you to sit by me."

He opened his briefcase, displaying a couple of red cylinders, wires and a battery, and demanded $200,000 in cash plus four parachutes. His demands were granted at Sea-Tac, where he released the 36 passengers and two of the flight attendants.

The plane took off again at his direction, heading slowly to Reno, Nevada, at the low height of 10,000 feet. Somewhere, apparently over southwestern Washington, Cooper lowered the aircraft's rear stairs and dove into a freezing rainstorm — a jump so daring that even some of the police who scoured the area reportedly said they hoped he got away.

No sign of Cooper has ever emerged, but a boy digging on a Columbia River beach in 1980 found three bundles of weathered $20 bills — Cooper's cash, according to the serial numbers.

But now, Marla Cooper, from Oregon, claims to have the first 'concrete evidence' in the case.

Relying on childhood memories, she recalled that her uncle Lynn Doyle Cooper had arrived at a family home in Oregon with serious injuries and that she overheard him talking about the hijacking.

Cooper says she's optimistic the FBI will be able to match her uncle's fingerprints to those involved in the case. The agency has said DNA testing did not match samples on the hijacker's necktie, but that the finding did not necessarily rule out the lead.

"It looks rather promising that this case could very well be solved in the next few months," Marla Cooper said.

Other Cooper enthusiasts aren't so sure. Agents discovered numerous partial fingerprints on an in-flight magazine, but it's unknown if any of those was Cooper's. He appeared to be careful not to leave fingerprints and demanded the flight attendant return the bomb note he had given her.

Partial DNA samples were recovered from the plane, including on the clip-on tie that was left on the hijacker's seat, but no one knows if the samples came from Cooper. The items that might have provided a definite DNA profile — the eight filter-tipped cigarette butts he chain-smoked during the flight — apparently went missing while in FBI storage in Las Vegas.

Many people, including Ralph Himmelsbach, the FBI's lead agent on the case until his retirement in 1980, believed Cooper could not have survived.

The temperature at 10,000 feet was 7 below zero, not including the minus-70 wind chill, and even if he survived the jump, he probably landed in the Columbia River or in rugged, wooded mountains at the onset of winter with no outdoor gear.

Tom Kaye, a paleontologist at the University of Washington's Burke Museum, said his presentation at the symposium will suggest Cooper lived. The three bundles of money that were found on the Columbia River beach at Tena Bar were about 20 miles east — that is, upstream — of what Kaye believes was the plane's flight path.

If that's so, the bundles couldn't have gotten there 'without mechanical or human intervention', he said.

That the bundles of money were found together suggests they didn't wash down to that spot from a tributary upstream, as others have suggested, he argues.

With the FBI's blessing, Kaye's team (http://www.citizensleuths.com ) tested the tie and discovered the microscopic slivers of pure titanium. At the time, he said, titanium was much rarer than it is today.

Titanium alloys were used in aircraft parts, but pure titanium was found only at companies that made pure titanium or at chemical companies which used it because of its corrosion resistance.

Of course, that doesn't mean the hijacker worked at one of those companies. He could have purchased the tie at a thrift shop just before the flight.

Following the symposium, some participants plan to head 39 miles north to a familiar stomping ground — the Ariel Store and Tavern in Ariel, Wash., in the heart of Cooper country. The store, which has hosted an annual Cooper celebration for 22 years, has a replica of the chute Cooper used hanging from its ceiling.

It also has the sign from the aft stairwell warning not to open it during flight; the sign ripped off when Cooper opened the door and was found by a hunter many years later.

Bryan Woodruff, the 52-year-old son of the owner, said that a week before the 20th anniversary, a man stopped in the store and looked around. He was a dead ringer for the FBI's composite sketch of the suspect.

"There were 7 or 8 of us sitting there, and this guy come in and got a pop and a candy bar," Woodruff recalled.

"The guy said he was travelling from Portland to Seattle for business, but why would he come out 10 miles from the highway to get a pop and a candy bar? We just all sit here going, wow, was that him?"

The man hasn't been back since.