On the afternoon of 24 November 1971, an unidentified man boarded a Boeing 727 and hijacked it in United States airspace.
Upon buying the ticket from the Northwest Orient Airlines counter with cash, the man identified himself as 'Dan Cooper' and the case became known ever since as the D.B. Cooper Hijacking.
The plane he boarded was flying to Seattle, Washington, and he had a one-way ticket.
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Once in the air, Cooper made cabin crew aware that he had a bomb before parachuting out of the plane with no one knowing what happened to him - even the FBI.
According to the FBI, when the man - who appeared to be in his mid-40s, wearing a business suit with a black tie and white shirt - got on the plane he ordered a bourbon and soda as the passengers waited to take off.
Shortly after 3pm, he gave a member of the cabin crew a note which explained that he had an explosive device in his briefcase and wanted her to sit with him.
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After showing her the bomb, he demanded she write down what he told her and soon after she took a note to the cockpit which demanded four parachutes and $200,000 (£148,000) in twenty-dollar bills.
According to reports, that would be worth around $1.3 million in 2021 (£965,000).
The flight successfully landed in Seattle and D.B Cooper exchanged the 36 passengers on board for the money and parachutes. He kept several crew members behind and the plane set off once more.
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Heading for Mexico City, he ended up jumping out of the back of the plane at around 8pm with a parachute and the money but disappeared into the night with no one knowing whether he ever survived.
The FBI was informed of the goings-on during the flight and an investigation was opened right away.
It went on to last many years with hundreds of people interviews, leads tracked across the country and an aircraft that was checked top to bottom for evidence.
On top of that, there were over 800 suspects and everyone, bar 24, was eliminated from consideration.
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According to the FBI, one person from the list - Richard Floyd McCoy - was and still is their favourite suspect. He was arrested for a similar hijacking less than five months later but he didn't match the physical descriptions of Cooper provided by two flight attendants.
Another theory is that Cooper fell to his death as the parachute he was using couldn't be steered, what he was wearing was unsuitable for a rough landing and he was heading for a wooded area at night time.
Fast forward to 1980 and a young boy discovered a rotting package of twenty-dollar bills which matched the serial numbers on the money.
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Then in July 2016, the FBI issued a statement saying it had 'redirected resources allocated to the D.B. Cooper case to focus on other investigative priorities'.
It's been 50 years since Cooper pulled off his mastermind robbery and the FBI aren't any closer to piecing together what actually happened. Only time will tell, I guess.
Featured Image Credit: Granger Historical Picture Archive/Alamy Stock PhotoTopics: News, Interesting, FBI, D.B. Cooper