A team of private investigators who spent years trying to crack the D.B. Cooper case claimed Thursday they decoded a letter from the hijacker revealing his identity.

The team, led by documentary filmmaker Thomas Colbert, claims that a letter sent to “The Portland Oregonian Newspaper” contains a confession from Army veteran Robert Rackstraw.

The letter was sent months after a man only identified as Cooper hijacked a Seattle-bound flight and parachuted out of a plane with $200,000 and never to be heard or seen from again.

“This letter is too [sic] let you know I am not dead but really alive and just back from the Bahamas, so your silly troopers up there can stop looking for me. That is just how dumb this government is. I like your articles about me but you can stop them now. D.B. Cooper is not real,” the letter reads. “I want out of the system and saw a way through good ole Unk. Now it is Uncle’s turn to weep and pay one of it’s [sic] own some cash for a change. (And please tell the lackey cops D.B. Cooper is not my real name),” the letter continued.

Colbert told The New York Daily News that he received the letter after suing the FBI for the files. He said he noticed that the letter was written in a similar fashion to a separate letter and he called a codebreaker to decipher it.

Rick Sherwood, a former Army Security Agency member, told the newspaper he spotted similarities with the words “D.B. Cooper is not real,” “Unk” or “Uncle,” “the system,” and “lackey cops.” Sherwood decoded “through good ole Unk” to mean “by skyjacking a jet plane” using a system of letters and numbers.

Colbert said the words “And please tell the lackey cops” meant “I am 1st LT Robert Rackstraw.”

"I want out of the system and saw a way through good ole Unk. Now it is Uncle’s turn to weep and pay one of it’s [sic] own some cash for a change." — DB Cooper

“I read it two or three times and said, ‘This is Rackstraw, this is what he does,’” Sherwood told The New York Daily News, adding that the writer was taunting authorities like he normally does. “I was definitely shocked his name was in there. That’s what I was looking for and everything added up to that,” Sherwood said.

Colbert claimed in February that he believed Cooper was a CIA operative whose identity had been covered up by federal agents. He told the Seattle PI that his team made the connection from work a code breaker uncovered in five letters allegedly sent by Cooper.

He claimed in a January interview that Cooper was Rackstraw. Colbert said at the time that several people who knew Rackstraw have come forward to claim he had possible connections to the CIA and other top-secret operations.

The investigator told Seattle PI the man who sent the letter may have put the codes into a letter to signal to possible co-conspirators that he was alive.

Rackstraw, 74, of San Diego, served in Vietnam. Colbert said in a press release Thursday that Rackstraw served in two of Sherwood’s units, has Special Forces paratrooper training, is an explosives expert and is a pilot with nearly two dozen aliases. Colbert said the FBI cleared Rackstraw in 1979.

In May, a Michigan publisher said the hijacker was former military paratrooper and intelligence operative Walter R. Reca. The publisher cited audio recordings that claimed Reca was speaking about the heist.

In 1971, on the night before Thanksgiving, a man calling himself Dan Cooper, wearing a black tie and a suit, boarded a Seattle-bound Boeing 727 in Oregon and told a flight attendant he had a bomb in a briefcase. He gave her a note demanding money. After the plane landed, he released the 36 passengers in exchange for $200,000 in ransom and parachutes. The ransom was paid in $20 bills.

The hijacker then ordered the plane to fly to Mexico, but near the Washington-Oregon border he jumped and was never seen or heard from again.

Despite the claims of the publishing company, the FBI has never ruled out the possibility that the hijacker was killed in the jump -- which took place during a rainstorm at night, over rough, wooded terrain. The hijacker's clothing and footwear were also unsuitable for a rough landing.

Fox News’ Travis Fedschun, Robert Gearty and Paulina Dedaj contributed to this report.