Newly released FBI files have revealed fresh details into the hunt for a man who hijacked a plane and parachuted to freedom with more than $300,000 in ransom money.
No one has ever been arrested in connection with the 1971 case, which remains the only unsolved airplane hijacking in US history.
It remains unknown whether the man responsible — later dubbed "DB Cooper" by media — even survived his escape.
The 398-page case file includes hundreds of tips, suspect profiles, and more information about a hoax which conned tens of thousands of dollars from a newspaper editor.
'Miss, you'd better look at that note — I have a bomb'
From the beginning, the hijacker was polite, quiet and inconspicuous.
On November 24, 1971, he bought a ticket on Flight 305 to Seattle at the Portland International Airport, paying in cash.
The ticket stub identified him as "Dan Cooper".
Witnesses described him as a white male in his mid-40s wearing a dark suit and black tie, carrying a black attaché case.
The flight was what was known at the time as a "puddle jumper" — just 30 minutes in the air between Portland and Seattle, a routine trip.
Onboard, Cooper took a seat in the last row, ordering a bourbon and soda while passengers waited for take-off.
He had not removed his sunglasses.
The plane took off at 2.50pm — about 10 minutes later, Cooper handed a note to one of the flight attendants.
"Miss," he said, after the woman — assuming it was a phone number from a love struck businessman — dropped the note unread into her purse.
"You’d better look at that note. I have a bomb."
For good measure, he opened the briefcase to show her several red cylinders, connected by a wire.
[map] Cooper wanted $US200,000 ($305,910), an amount equal to $US1,591,781 ($2,434,697) in today's currency.
He wanted it in a "knapsack" by 5pm. He also wanted two sets of parachutes — implying he intended to take a hostage.
The plane would land at the Seattle-Tacoma International Airport and there the money would be brought aboard, Cooper told the flight crew.
Then, and only then, would the 35 passengers be free to go.
A leap from a plane launches a decades-long FBI manhunt
Ultimately the plane circled Seattle for two hours — during that time, many passengers later told media they didn’t even know what was going on.
Richard Simmons, head of a prisoner-rehabilitation program, told reporters he "slept most of the time we were up there".
"I saw one stewardess answer a call and her face dropped," he said.
“She looked bewildered and gulped. I guess she learned what was happening then.”
His wife, Barbara, worried they may have gotten on the wrong plane.
"First we went right past Seattle, then Everett," she said.
"All I could think of was the plane was going to Vancouver and we were on the wrong flight."
On the ground, the FBI and the Seattle Police Department rushed to get the money, parachutes, and emergency personnel ready for the landing.
The plane landed at 5.46pm, and the money was handed over by an airport staffer — 10,000 unmarked $20 bills in a cloth bag.
The passengers got off. The flight attendants retrieved the parachutes. He told them he didn’t need the instructions on how to use them.
The plane took off again a few hours later with only Cooper and the flight crew aboard, followed by three fighter jets.
This time it was heading for Mexico City, but the hijacker would not make it that far.
As the plane travelled somewhere between Seattle and Reno around 8pm, Cooper ordered the flight attendants to open the staircase at the back of the plane.
Then he tied the bag of money around his waist, donned his parachutes, and jumped.
It was the end of the hijacking, but only the beginning of an investigation that would continue for decades.
Suspects, interviews and a $30,000 hoax
The new files released this month are the latest in a series to be declassified under the Trump administration.
The first lot of more than 400 pages were published online in March.
The documents, at times heavily redacted, outline leads and suspects pursued by the FBI over the years.
At one point, a man in a wheelchair became their key suspect, only to be ruled out.
"It is believed that the hijacker in this case has full use of all of his extremities and witnesses did not tell of any physical disability," the agent wrote.
"A man confined to a wheel chair [sic] did not hijack the plane in this case."
Other men investigated included former pilots and members of multiple different skydiving clubs who bore a resemblance to Cooper.
Men who did not resemble the artist’s sketch but who had mentioned "different ways to hijack an airplane" or suggested "the way to hijack [and] escape would be … using a parachute" were also reported to police.
Several documents include long and redacted lists of suspects whose photographs were shown to witnesses without success.
A contributing editor for Newsweek magazine, Karl Fleming, told the FBI he had placed an ad in multiple newspapers asking DB Cooper to contact him.
The ad included his home phone number.
He said he had been contacted and met multiple times with a man who identified himself as Cooper.
At one point, he said he had been shown several $20 bills he said he was "98 per cent positive" matched copies of the ransom money shown to him by an unknown source.
He handed over $US30,000 ($45,810) for the exclusive interview, publishing a three-part series detailing "Cooper’s side" of the story.
Two men were later convicted and sentenced to serve time in federal prison for impersonating Cooper and pocketing the money.
The rest of the files do not draw any definitive conclusion.
'DB Cooper, Where Are You?'
In the years since the hijacking, the story has become part of American pop culture history.
By 1972, T-shirts bearing the phrase "DB Cooper, Where Are You?" were already appearing in novelty shops across the west coast.
There have been dozens of fiction and non-fiction books about the case, as well as references in film and television.
In David Lynch’s 1990 TV series Twin Peaks, the main character is named Dale Bartholomew Cooper — a nod to the now infamous hijacker.
More recently, DB Cooper was revealed to be Loki in the Disney+ series Loki, set in the Marvel Cinematic Universe.
An annual "CooperCon" convention is held in Seattle, letting Cooper enthusiasts and researchers swap theories.
None of it has led to any answers.
Max Shaffer, then chief of security for the Seattle region of the Federal Aviation Administration, told the New York Times in 1972 he believed Cooper was dead.
"I feel that one of these days some hunter in Oregon or Washington is going to find the skeleton of this man," he said.
As of July 12, 2016, the FBI had officially ended their investigation, leaving it as one of the longest cold cases in the agency’s history.
"The mystery surrounding the hijacking of a Northwest Orient Airlines flight in 1971 by a still-unknown individual resulted in significant international attention and a decades-long manhunt," they said in a statement.
"Evidence obtained during the course of the investigation will now be preserved for historical purposes at FBI Headquarters in Washington, DC."
