A new report claims that the FBI knew the true identity of notorious hijacker DB Cooper but says senior executives in James Comey's administration were involved in a scheme to 'conceal, suppress and fabricate' evidence in the cold case.

In November 1971, a 'non-descript man' identifying himself as Dan 'DB' Cooper bought a $20 ticket for a Northwest Orient flight from Portland to Seattle, later demanding $200,000 ransom and a parachute in what would become one of the most infamous cold cases of all time – and the only unsolved skyjacking in US history.

Cooper would later vanish without a trace, skydiving from the rear of the plane with the cash in hand and prompting decades of debate and conspiracy over the brazen thief's true identity.

An unexpected breakthrough came last year when cold case expert and author Thomas J Colbert identified Robert Rackstraw, a military vet with a murky past who died in July aged 75, as the man responsible.

FBI documents obtained under the Freedom of Information Act following Rackstraw's death show that he was a prime suspect for the Bureau.

Robert Rackstraw (left), a military vet with a murky past riddled by fraud and con-artistry, died last month and is believed to be legendary 1971 skyjacker DB Cooper (composite seen right)

Investigator Tom Colbert claims the FBI. under James Comey's administration, knew Rackstraw was DB Cooper but were involved in a scheme to 'conceal, suppress and fabricate' evidence in the cold case

Rackstraw, who served in Vietnam, was forced to resign from the Army in 1971 and according to FBI dossiers from 1978, he was 'extremely bitter over his severance.'

Indeed, when the Bureau questioned Rackstraw in 1978, 'he admitted to the arresting agent that he would be fully capable of successfully effecting the NORJAK hijacking [the FBI's code-name for the crime].'

According to the FBI document Rackstraw had written angrily to the military following his honorable discharge, 'in lieu of elimination because of unfitness or unacceptable conduct'.

Rackstraw wrote: 'I can only hope that I will never use the training and education the Army gave me against the Army itself, as I would be a formidable advisary [sic].'

Colbert claims that retired Assistant FBI Director Tom Fuentes, now a CNN commentator, was a key figure in the alleged cover up.

The newly released files also reveal that Rackstraw had told his sister, Linda Loduca, he was working for a real estate firm in Los Angeles upon his return to the States.

As part of his job he was selling land in Oregon, 'back in an area so remote that there were no roads,' Loduca told the Bureau, 'and Robert had to fly prospect there to see the land.'

In one previously classified paper, the investigating officer writes: 'Rackstraw has been suggested as a suspect in this matter because he resembles the artist's composite ... and because of his military background particularly his paratrooper training.

'He appears to be fully capable of successfully affecting the NORJAK hijacking.'

Now Colbert is naming at least four of former FBI director James Comey's senior executives who, he claims, knew Rackstraw was the infamous Cooper but were involved in a scheme to cover it up.

Colbert claims that retired Assistant FBI Director Tom Fuentes, now a CNN commentator, was a key figure in the alleged cover up.

He claims that between the launches of the Hillary Clinton email investigation and Trump's Russia probe in 2016, a volunteer cold case team alerted the FBI it had determined Rackstraw was the missing 1971 outlaw D.B. Cooper.

Copies of the typewritten letter were sent to The Seattle Times, The New York Times, The LA Times and The Washington Post by the hijacker at the time

Fuentes was commissioned to study the team's evidence for three days and says Fuentes was impressed with their research - stating in a recorded transcript that it was 'a tremendous circumstantial case' and 'very probably is [Cooper].'

But, Fuentes' endorsement reportedly set off Comey's office, which resulted in his team cancelling their collaboration with the independent investigative team.

The FBI senior executives allegedly canceled a 2016 meeting to accept the independent team's forensic materials, that included DNA, and 'discretely shipped off the Cooper file to a locked archive'.

'Then the senior agents – including Fuentes – proceeded to down-play, hide and lie about the ''tremendous'' Rackstraw evidence in the national media,' the report claims.

Colbert says Jim Reese, one of the investigation team's 13 retired FBI agents, summarized it best: 'Rule #1 was you don't embarrass the Bureau. This door-slam was politics, pure and simple.'

Colbert names three separate instances where national news networks abruptly pulled stories that presented his research before they aired.

The first, he claims, came in September 2016 when a Good Morning America reporter phoned Colbert for an interview on the Cooper case.

Rackstraw was a veteran with extensive military training, serving in the National Guard, the Reserve, the Army, and served in one of the most decorated combat divisions in the US Army, the 1st Calvary Division, in Vietnam in 1969

A tie left behind by DB Cooper on the plane helped to eliminate several hundred suspects of the FBI investigation, following DNA tests

The package was edited, but 'inexplicably shelved' for broadcast.

NBC News showed interest in the story twice in 2018 and had members from the independent investigation interviewed, but again, the stories were killed before airtime.

Rackstraw was a veteran with extensive military training, serving in the National Guard, the Reserve, the Army and served in one of the most decorated combat divisions in the US Army, the 1st Calvary Division, in Vietnam in 1969.

He was first considered as a suspect seven years after the hijacking in 1978, with investigators saying 'so many things' about him seemed to match the description of Cooper.

Rackstraw was interviewed about his link to the case in 1979, where he was asked explicitly to state whether he was or wasn't DB Cooper.

With a wry smile visible across his face, he told the KNBC reporter, 'Uh, I'm afraid of heights'.

The reported added that his parachute training in the military means he 'could've been DB Cooper'.

'Could have been, could have been,' Rackstraw responded.

Little came of the FBI's suspicions of Rackstraw, but Thomas Colbert officially pointed the finger of blame at him in June last year, wielding a letter sent to the Portland Oregonian newspaper at the time, said to reveal him to be Cooper.

The hijacked Northwest Airlines jetliner 727 sits on a runway at Tacoma International Airport, Seattle on November 25, 1971

Badly decomposed $20 dollar bills were found near where Cooper is said to have landed. A check of their serial numbers showed that they were identical to the bills given to hijacker D.B. Cooper on November 24, 1971

'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,' he writes. '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).'

Colbert said he obtained the letter after successfully suing the FBI for access to the Cooper files. He gave the letter to Rick Sherwood, a former member of the Army Security Agency, to decode.

Colbert is adamant the FBI was too hasty to wrap up the investigation and now says the revelation of the hidden messages, especially the links to the CIA, proves why the agency has been stonewalling.

He said his team found what they believed to be a parachute strap and foam padding from skydiver's backpack in the forest near Cooper's alleged jump location in 2017.

They turned over the two items, along with the dig site itself, to the FBI.

Colbert believes the FBI still hasn't taken action on any of the team's efforts despite what they provided them.

He has spent several years conducting his own investigation into the mysterious crime, writing a book and producing a documentary series on it in the process.

Colbert said he has extensively investigated Rackstraw as well. In 1977, six years after the hijacking, Rackstraw was suspected of kiting checks for $75,000, but fled before arrest and went to Iran to teach the Shah's men how to fly helicopters.

FBI documents obtained under the Freedom of Information Act