Sheridan Peterson, right, was a lead suspect in the DB Cooper affair. Photo / Supplied
Sheridan Peterson, right, was a lead suspect in the DB Cooper affair. Photo / Supplied
Few cases in history have been able to stump America's most experienced investigators.
Yet the unsolved mystery of how a well-groomed businessman-type successfully hijacked a flight from Portland, Oregon to Seattle, Washington 50 years ago – only to parachute from the plane after his demands were met, never to beseen again – baffled the FBI to such a degree authorities decided to close the book on it years ago.
The odds of them ever solving the puzzle are even slimmer now: Sheridan Peterson, one of the lead suspects thought to be "Dan 'DB' Cooper", died on January 8, according to memorial website Legacy.com, taking any secrets about the case to his grave.
The 94-year-old California resident once went to far as to claim that "the FBI had good reason to suspect me" in a July 2007 article for the National Smokejumper Association's (NSA) Smokejumper Magazine.
A Northwest Boeing 727 was hijacked in the daring robbery. Photo / Airline Fan, CC
"Friends and associates agreed that I was without a doubt DB Cooper. There were too many circumstances involved for it to be a coincidence," he wrote.
"At the time of the heist, I was 44 years old. That was the approximate age Cooper was assumed to have been, and I closely resembled sketches of the hijacker."
Even Mr Peterson's ex-wife once told FBI agents, within weeks of the November 24 incident, that it "sounded like something he'd do".
On a separate occasion, a photo came to light from a Boeing newsletter showing Mr Peterson dressed in exactly the same manner – a black raincoat over a freshly-pressed business suit – as the hijacker was said to have been during the 1971 flight.
"What was even more incriminating was the photo of me simulating a skydiving manoeuvre for Boeing's news sheet," Mr Peterson wrote in his Smokejumper piece.
A character fit was published by the FBI shortly after the hijacking. Photo / Wikimedia Commons
"I was wearing a suit and tie – the same sort of garb Cooper had worn, right down to the Oxford loafers. It was noted that skydivers don't ordinarily dress so formally."
Phoenix entrepreneur Eric Ullis, who followed the case for years, previously said he is "98 per cent sure" Mr Peterson is the man behind the daring heist.
According to Mr Ullis, Mr Peterson "literally worked in the department that wrote the manual for the Boeing 727 jet" – the same plane DB Cooper made his daring jump from.
Mr Peterson long claimed, however, that at the time of the hijacking he was living in a mud hut in Nepal, working on a "protest novel" about his experiences in Vietnam.
What happened on 24 November, 1971
On November 24, 1971, a man identifying himself as Dan Cooper approached a Northwest Orient Airlines booth at Portland International Airport.
He was carrying a black briefcase and bought a $20 one-way ticket on Flight 305 to Seattle, Washington. It was a 30-minute journey.
Upon boarding the Boeing 727-100, the passenger sat in seat 18C at the back of the passenger cabin. He ordered a bourbon and soda, and lit a cigarette.
The flight with 36 passengers on board took off on schedule at 2.50pm.
Mr Cooper passed a note to a flight attendant. Assuming he was just another smooth gentleman hitting on her, she slipped the note straight into her coin purse.
The pilot was informed of the demands and Northwest Orient's president, Donald Nyrop, approved the payment of ransom to Mr Cooper in exchange for the safety of all passengers on board.
The crew was ordered to co-operate and passengers were informed a slight technical issue would delay their landing.
Mr Cooper was said by all witnesses to be a calm, polite and well-spoken man. He offered to request meals for all the crew members and would sit back and sip his bourbon before settling his drink bill.
FBI found portions of the discarded ransom in 1980. Photo / FBI
By 5.24pm his demands were met and the aircraft landed 15 minutes later in Seattle — two hours after its scheduled landing time. The pilot was told to take the jet to an inconspicuous part of the tarmac and turn off the lights so as to not attract police snipers
After the backpack with cash and parachutes were delivered, and while the plane was being refuelled, all passengers and cabin crew were asked to leave the aircraft.
The flight deck crew remained and Mr Cooper advised them of his plan — they had to fly toward Mexico City at the minimum airspeed, at an altitude of 10,000 feet and the cabin had to remain unpressurised.
Somewhere over the lower Cascade mountains in Washington, Mr Cooper, wearing a parachute and with the ransom cash strapped to his body, stepped out of the plane.
The FBI have always maintained Mr Cooper didn't survive his risky jump – the only thing that has ever been found is a portion of the stolen money — three packets of cash, which totalled $5800, were discovered on the Columbia river in 1980 — and his cheap, black clip-on tie.
