A man who has spent years investigating the mystery of notorious criminal DB Cooper believes he has unearthed 'a compelling person of interest'.
On 24 November, 1971 a mysterious man who claimed to be carrying a bomb hijacked Northwest Airlines Flight 305.
He received a ransom of $200,000 (over £1 million in today's money) not to detonate his supposed explosives and after getting his money he donned a parachute and leapt out while the plane was in mid-flight.
The man, who had been known as DB Cooper, was never found and all that remained of him was a clip-on tie he'd left behind.
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Only those who were on board the plane at the time really got a good look at him, and even then on the final leg of his journey when he jumped out of the plane he made flight attendant Tina Mucklow and the rest of the crew stay in the cockpit.
While a small portion of his ransom money was found in 1980, investigations into the identity of DB Cooper have never decisively nailed down who he actually was.
However, Eric Ulis has spent years trying to solve the mystery behind DB Cooper's identity and believes he has tracked down a new lead into the truth behind the mystery man.
Since the hijacker left a tie behind and modern forensics have advanced to a point where we can learn so much from so little evidence, Ulis says he has identified traces of stainless steel and titanium.
This pointed him towards a Pennsylvania factory named Crucible Steel, which supplied many of the materials aircraft manufacturer Boeing used to build their aircraft.
The plane Cooper hijacked was a Boeing 727 and during his crime he displayed a working knowledge of the aircraft, including knowing that the plane's rear steps could be lowered while the plane was in flight.
Ulis therefore reckons that new testing makes research engineer Vince Peterson, who died in 2002, the most likely man to be DB Cooper.
Speaking to Fox News, Ulis said Peterson's job would have given him knowledge of how the plane worked, and that Boeing had a 'significant downturn' in 1971 which may have affected the man's livelihood.
Crucible Steel workers also often travelled to Seattle due to their connection to Boeing, and the flight DB Cooper hijacked was heading there.
He said: "I can put him in Seattle, I can put him at Boeing.
"He’s a compelling person of interest. He’s definitely someone I’m going to continue to dig into."
Topics: Crime, Science, True Crime, US News, DB Cooper
Joe Harker