The D.B. Cooper case has baffled the FBI for 45 years. Now it may never be solved.

Out of all America's skyjackings, only one remains unsolved.

The case has confounded FBI investigators for decades -- its astonishing details, clues and alleged participants have become the stuff of American criminal lore.

The story has inspired songs, t-shirts and books and the main character has, at times, bordered on American folk hero status.

Now, after one of "the longest and most exhaustive investigations" in FBI history, the agency is finally moving on from the search for the infamous skyjacker known as D.B. Cooper, according to a statement released by the FBI.

The riveting search -- which Washington Post reporter Cynthia Gorney described as "Jesse James meets the Loch Ness monster" -- is more or less over.

"During the course of the 45-year NORJAK investigation, the FBI exhaustively reviewed all credible leads, coordinated between multiple field offices to conduct searches, collected all available evidence, and interviewed all identified witnesses," the statement says, referring to the phrase "Northwest hijacking."

"Over the years, the FBI has applied numerous new and innovative investigative techniques, as well as examined countless items at the FBI Laboratory."

"Evidence obtained during the course of the investigation will now be preserved for historical purposes at FBI Headquarters in Washington, D.C." the statement adds.

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Never seen again

The case began on the afternoon of Nov. 24, 1971, when a man who went by the name D.B. Cooper used cash to buy a one-way ticket on Flight 305, bound for Seattle, according to an FBI statement.

By the end of night, Cooper would vanish into thin air 10,000 feet above dense Washington State forestland with $200,000 in cash, appearing to pull off a heist so daring that he would eventually be considered the most infamous hijacker in American history.

The FBI describes Cooper as a "quiet man" in his mid-40s who wore a business suit with a black tie and white shirt. After ordering a bourbon and soda, he passed a note to a stewardess that explained he had a bomb in his briefcase.

"The stunned stewardess did as she was told," the FBI statement notes. "Opening a cheap attaché case, Cooper showed her a glimpse of a mass of wires and red colored sticks and demanded that she write down what he told her. Soon, she was walking a new note to the captain of the plane that demanded four parachutes and $200,000 in twenty-dollar bills."

After landing in Seattle, Cooper allowed 36 passengers to leave the plane in exchange for cash and several parachutes. He instructed the plane to take off again and head for Mexico City.

A little after 8 p.m., between Seattle and Reno, according to the FBI, Cooper launched himself from the back of the plane with his money in hand.

He was never seen again.

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'Odd uncle'

Originally, FBI investigators believed Cooper must have been an experienced skydiver, possibly with military experience.

"We concluded after a few years this was simply not true," Special Agent Carr said in 2007. (The FBI didn't provide his first name.) "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."

In Gorney's 1980 profile of Ralph Himmelsbach -- the FBI's lead investigator on the case at the time -- the aging lawman disputed the romantic idea that Cooper was a Robinhood-esque figure who gamed the system by pulling off an exquisite victimless crime.

"'Sleazy' is the word the he uses, actually. A sleazy, rotten criminal." (Himmelsbach turns downright eloquent when he gets going on this subject.) "Nothing heroic about him, nothing glamorous, nothing admirable at all. He jeopardized the lives of 40 people and I have no admiration at all. He was a stupid selfish. man . . ."

At the time, Gorney noted, Himmelsbach was fielding calls from all over the country and responding to mail from as far away as Germany and investigating just about everything in between, including examining pants "found slung on Washington treetops (hoax)," and chasing "after men too short and men too young and men whose alibis place them firmly far away from the Northwest skies that night."

"Well over a thousand," he told The Post, tallying up his Cooper suspects to date. "Real, real good ones; real, real poor ones. A lot of both. And many in between."

Nearly four decades and countless suspects later, not much has changed. Despite some tantalizing clues discovered over the years -- such as a rotting package full of $5,800 in twenty-dollar bills with serial numbers that matched the ransom money -- many investigators believe Cooper never survived his plummet to the earth.

Cooper's parachute wasn't steerable and he would've landed in the wilderness wearing a suit and dress shoes in the winter time, at night. Gorney described the area where the jump is thought to have occurred as "a God-forsaken swath of rugged Washington forest country."

"If there's any place around you wouldn't want to jump into, that'd be it," an FBI investigator told her.

Years later, Carr agreed: "Diving into the wilderness without a plan, without the right equipment, in such terrible conditions, he probably never even got his chute open.

At the time, the Seattle Times reported, Carr was renewing his plea for new information in the case, possibly with the help of technology.

While publicly brainstorming, he said he was hoping a clever hydrologist using satellite technology might find a way to trace the Cooper cash found on the Columbia River in 1980 back to the creek in which it originated.

At the end, he noted, a body might be waiting.

Perhaps, he said, somebody might remember something about an odd uncle.

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Almost a decade later, the thief remains at large.

"Although the FBI appreciated the immense number of tips provided by members of the public, none to date have resulted in a definitive identification of the hijacker," the FBI's latest statement says. "The tips have conveyed plausible theories, descriptive information about individuals potentially matching the hijacker, and anecdotes-to include accounts of sudden, unexplained wealth."

"Every time the FBI assesses additional tips for the NORJAK case, investigative resources and manpower are diverted from programs that more urgently need attention," the statement adds.