At first, Tina Mucklow didn't take much notice of the elegantly dressed man sitting in the back row as she was serving drinks on a flight shortly before takeoff.
While her colleague, Florence Schaffner, served passengers from the back of the main cabin, Tina was up front offering drinks.
But, as she made her way to her jump seat at the back to prepare for their flight, she noticed her colleague point to a piece of paper lying on the floor.
"Miss, I have a bomb here and I would like you to sit by me," said the passenger who had attempted to give Tina the note.
The man, dressed in a business suit, a pearl tie clip and horn-rimmed sunglasses, had bought a ticket on Northwest Orient Flight 305 under the name "Dan Cooper".
Later, an exhausted local journalist would mishear the name and report it as "DB Cooper", a moniker that lives on 50 years later.
Cooper had spent the time before takeoff sipping a bourbon and soda.
But things took a strange turn as the plane barrelled down the runway when he threatened to bring it down with the contents of his briefcase.
It was a cartoonish mess of wires, a timer and red sticks of dynamite.
Tina phoned the cockpit to inform the pilot of the situation, and then sank into the seat next to the mysterious passenger.
Cooper gave her his list of demands. He wanted $US200,000 — equivalent to about $US1.3 million today — four parachutes, and a fuel truck to be waiting when they landed in Seattle.
What followed on that day in November 1971 would turn Cooper into a legend.
His audacious crime remains one of the great unsolved mysteries of the 20th century.
The FBI officially gave up and closed the case years ago, but amateur sleuths continue to scrutinise every clue and every suspect.
For the past 50 years, DB Cooper has occupied a special place in American mythology: The well-dressed stranger who committed the perfect crime, fell from the sky and maybe, just maybe, got away with it.
Why no-one resisted the hijacker
The DB Cooper mystery occurred during what has been called "the golden era of hijacking".
"Desperate and deluded souls commandeered over 130 planes between 1968 and 1972, often at a pace of one or more per week," journalist Brendan I Koerner wrote in his book, The Skies Belong To Us.
It was usually more of an inconvenience than a tragedy, with the hijacker typically demanding a ransom and for the plane to be diverted to Cuba, where they could evade capture.
The problem got so bad that, in 1969, the US Federal Aviation Administration even considered building a fake Havana Airport where hijacked planes could land.
And, so, by the time the mysterious DB Cooper boarded a Boeing 727 on November 24, 1971, the US airline industry had a long-held policy of total compliance with hijackers.
The flight to Seattle from Portland only took 30 minutes, so authorities had the pilot circle the airport for several hours while they gathered DB Cooper's cash and parachutes.
Other passengers, totally unaware their lives were in danger, were told a mechanical issue meant they had to dump some fuel at sea before landing.
After four hours of aimless circles over Seattle, the plane landed.
Once Tina had brought onboard the parachutes and cash — stacks of $20 bills weighing nine kilos all up — DB Cooper freed the passengers, who were still blissfully unaware they were hostages.
Then the hijacker revealed his real plan: The plane was to be refueled, and the crew was to take him to Mexico City where he could slip away.
Daring exit from 3,000 metres above ground
As the now-empty plane took off, Tina was still sitting next to the hijacker.
"I think the one feeling that was forefront in my mind was I just felt so alone," she told Rolling Stone this year.
Once they were back in the skies, Cooper had eerily precise instructions for the pilot.
He was to fly the Boeing 727 low, with the landing gear down, the wing flaps at 15 degrees, and the rear stairway lowered.
The Boeing 727, which Cooper had been so careful to choose as his target, was the only plane on the market with an "airstair" under the tail.
Only moments after they had taken off, Cooper asked Tina to show him how to open the staircase.
He wasn't going to Mexico after all.
Howling wind filled the cabin as Tina opened the door and directed Cooper to the stairs. She became terrified that she would be sucked into the night air when he opened them.
Instead, he asked her to go to the cockpit and join the pilots.
As she pulled the curtain across the aisle to give him privacy, Tina caught a glimpse of him tying something — perhaps the nine kilo money bag — around his waist.
"All of a sudden the cockpit door opened, and in walked this lovely lady who had been our passive resistance to the hijacker," copilot Bill Rataczak told Rolling Stone.
Tina and the pilots watched as a light flashed on the control panel indicated the airstair had been fully extended.
They did not know if they were free of the hijacker until they landed at nearby Reno Airport, and swarms of FBI agents boarded the plane.
The money, the parachutes and the hijacker were gone.
Somewhere over rugged forest, Cooper had jumped with a non-steerable parachute into driving rain and icy temperatures.
The hunt for DB Cooper
Police scoured south-west Washington for days, searching for what many presumed would be a body.
Cooper had parachuted into rugged wilderness in the middle of the night, dressed only in a suit and loafers.
Despite carrying out one of the most extensive searches in US history — even uncovering the bodies of two people who authorities had no idea were even missing — there was no trace of the hijacker in the woods.
Treasure hunters chartered a submarine to search the depths of Lake Merwin. Nothing was found.
As days turned to weeks, many started to wonder if DB Cooper not only stuck the landing, but trudged out of the forest with his loot.
"You know, it's funny, folks are actually pulling for this man," a local resident told New York Magazine in 1971.
"Like he's some kind of Robin Hood character. He wasn't some wild radical … He was you, or me, or your neighbour."
Tom Kaye — a palaeontologist who assembled a team of "citizen sleuths" for the FBI in 2009, to go over the case — said there was a good chance Cooper survived.
"If you were planning on going back to work on Monday, then you would need as much time as possible to get out of the woods, find transportation and get home," he said in his report.
"The very best time for this is in front of a four-day weekend, which is the timing Dan Cooper chose for his crime.
"He knew he had to hitchhike out of the woods, and it is much easier to get picked up in a suit and tie than in old blue jeans."
In 1980, a boy found part of DB Cooper's loot — $US5,800 in total — on the banks of the Columbia River.
But the discovery only deepened the mystery.
Who jumped out of the plane?
To this day, nobody knows who "Dan Cooper" was, or if that was his real name.
The only item the mysterious man had left behind after his daring escape was a black tie with a distinctive pin.
Investigators and crime enthusiasts have combed through Tina's recollections for clues.
Out of the four parachutes he had on offer, his choice of an older, non-steerable model is a subject of intense debate.
Does it mean he was an amateur, who passed over the more modern parachutes because he had no idea what he was doing, and likely tumbled to his death?
Or does his choice suggest Cooper was an ex-military paratrooper with dozens of jumps under his belt in far more treacherous conditions than the forests of America's Pacific North-West?
The list of possible suspects quickly grew to the hundreds — including a man with the initials DB — but nothing concrete emerged.
As authorities whittled down the names of those who could have pulled off the stunt, only a handful remained the favourites. None has ever been charged.
One theory is that Richard Floyd McCoy, a Morman school teacher, was the man authorities were looking for.
He was first brought to the FBI's attention by his former roommate in the National Guard.
They had tipped the FBI off about McCoy's involvement in a similar hijacking stunt pulled off in Denver, just five months after the Northwest Orient hijacking.
But the nearly identical physical descriptions of Cooper provided by two flight attendants did not match McCoy's appearance, according to the FBI, and he was ultimately ruled out.
Others have pointed to Sheridan Peterson as another possibility because of his experience as a firefighter who parachuted into bushland.
Decades after the heist, Peterson recalled how he came home one day to find a note pinned to his door by FBI agents. "Please call, thank you," it said.
There were a few reasons why Peterson had come to their attention. He was 44 years old at the time of the heist — approximately the same age Cooper was assumed to have been.
And he was photographed wearing a suit and tie in Boeing magazine — attire that was rare for skydivers.
"The FBI had good reason to suspect me. Friends and associates agreed that I was without a doubt DB Cooper," he wrote in Smokejumpers magazine.
"There were too many circumstances involved for it to be a coincidence."
However, Peterson claimed, he was in Nepal at the time of the hijacking and provided DNA samples to the FBI.
In his view, DB Cooper would not have survived the fall.
"DB did everything wrong. First of all, he picked up the pilot's chute instead of the skydiving rig," he wrote.
"Falling at an estimated speed of over 100 miles per hour, the canopy's opening shock would have been devastating. Skydiving rigs are packed in such a way that they open gradually, lessening the opening shock."
DNA samples, pulled from DB Cooper's tie, have also ruled out other suspects over the years. As the decades elapsed with no further clues, the FBI finally closed the book on the case in 2016.
Why DB Cooper became a legend
Authorities may have moved on but there remains a committed number of amateur sleuths hoping to unmask the hijacker.
In the documentary, The Mystery of DB Cooper, John Dower sought to shed light on the people who have spent their lives following the hijacking and their ideas on who might be behind it.
Each theory seems plausible, like Jo Weber, who believes her late husband Duane was DB Cooper after he confessed he was the hijacker on his death bed.
Another woman Marla Cooper, suggests her uncle was behind it.
But after a four-year hunt for answers, John Dower said he found himself becoming like the subjects in his documentary.
His obsession had led him down the rabbit hole, and his health couldn't take it any longer.
"Documentarians, we're supposed to be, I guess, objective, and somehow stand above it all," Dower told Vanity Fair last year.
"I mean, I tried— but I became one of them. It was unavoidable. I became obsessed."
In his view, the case had endured and captured people's imagination because it's still an enigma.
The hijacker's fate is open to debate. Perhaps he paid the ultimate price for his reckless crime. Or perhaps he got away with it.
We may never know the answer and, for that reason, the mystery of DB Cooper lives on.
