By Steve Olafson
OKLAHOMA CITY (Reuters) - A woman claiming to be the niece of the mysterious skyjacker dubbed D.B. Cooper, who bailed out of a jetliner 40 years ago with $200,000 in ransom, says she recalls her uncle plotting the sensational caper at a family gathering in 1971.
Marla Wynn Cooper, 48, of Oklahoma City, said on Wednesday that she was the person who furnished investigators new clues to a previously unknown suspect, sparking a renewed probe of a case the FBI counts as the only unsolved hijacking in U.S. aviation history.
The woman told Reuters she gave the FBI a leather guitar strap made by her uncle, now dead for over a decade, along with a photo of him with the same strap, to be examined for fingerprints that might match those from the plane.
"They were never going to close this case without someone knowing the truth," she said, adding she underwent a polygraph test administered by the FBI to assess her credibility.
The FBI has acknowledged that a leather guitar strap was submitted as evidence in the case, but to no avail.
"The material wasn't suitable for extracting fingerprints from, so we're in the process of obtaining other times that may provide a better source of comparison prints," Fred Gutt, a special FBI agent based in Seattle, said on Wednesday.
He declined again to reveal the person who came forward with the latest information, saying, "We do not identify witnesses in an investigation." The FBI said earlier this week its latest lead came from someone "close" to the new suspect.
But Marla Cooper said she is certain that her uncle, Lynn Doyle Cooper, who went by the name L.D. Cooper, was the man who seized a Seattle-bound Northwest Orient Airlines flight in November 1971 by claiming to have a bomb. He vanished when he jumped from the rear of the plane in mid-air with a parachute and $200,000 in cash, which he had ransomed from the airline in exchange for the release of the 36 other passengers.
The plane was flying at about 10,000 feet at night through a storm over wooded, rugged terrain in the Pacific Northwest, and the hijacker was presumed by many to have perished.
The sensational Thanksgiving eve caper triggered a massive manhunt, and the FBI went on to consider over 800 suspects in the first five years after the crime.
The only trace from his getaway was a crumbling batch of $20 bills matching the ransom money's serial numbers, unearthed by a boy from a sandbar along the Columbia River in 1980.
Marla Cooper, a sales executive for a coffee company, said she decided to come forward as a matter of civic duty after piecing together vague childhood memories that were reinforced by comments her parents made to her in more recent years.
In an interview at a downtown Oklahoma City restaurant, she recalled seeing L.D. Cooper engrossed in suspicious behavior with another uncle, Dewey Cooper, during a holiday gathering at her grandmother's house in Oregon before Thanksgiving 1971.
She said the two men, both brothers of her father, appeared to be secretly planning something as they experimented with sophisticated walkie-talkies, then left the family gathering for what they said was a turkey hunt.
They returned Thanksgiving Day with her uncle bloodied and bruised, claiming he had been in an automobile accident.
"I looked in the car ... for a turkey, and what I see instead is my uncle injured," she said. "I started to cry and said, 'What happened?' They told me they'd been in a car wreck, and I said, 'The car is fine. What were you driving?' My uncle Dewey said, 'Marla, shut up. Go get your dad."
Later while eavesdropping, Cooper said, she overheard her Uncle Dewey say, "'Our money problems are over. We just have to go back and get the money. L.D. hijacked the airplane.'"
Four decades later Marla Cooper says she is the only person alive who witnessed these interactions and remembers her father "admonished me to never talk about any of this."
She said her uncle served in the Korean War, though he was not a paratrooper, and she believes he suffered post-traumatic stress disorder, drank heavily and took a lot of medication.
"My uncle was a bit of a lost soul," she said, recounting that he usually wore black clothes but was her favorite of her father's four brothers.
She also recalled he was obsessed with a Canadian cartoon skydiving hero named Dan Cooper and even kept a Dan Cooper comic book tacked to a wall.
According to the FBI, the man in the dark business suit who hijacked Northwest flight 305 called himself Dan Cooper when he purchased a one-way ticket in Portland, Oregon, but the moniker D.B. Cooper originated from media reports and stuck.
Marla Cooper said she last saw her uncle L.D. around Christmas 1972, just over a year after the hijacking, and that he died in 1999.
She said she has started writing a memoir about her account and has been contacted by numerous literary agents.
(Writing and additional reporting by Steve Gorman; Editing by Greg McCune and Cynthia Johnston)