Full body scanners at America's airports may not be necessary to prevent terror attacks on aircraft, according to documents obtained from the Transportation Safety Administration by a self-described civil rights activist. In addition, as recently as 2011 the TSA believed that there was little, if any, threat to civil aviation from terror groups, the documents suggest.

The statements were obtained by Jonathan Corbett, a 28-year-old tech entrepreneur from Miami, who is on a one-man crusade to remove body scanners from airports.  Corbett, however, isn't against all security. He doesn't have a problems with the metal detectors and bomb-sniffing dogs - just the scanners and pat-downs.

Corbett, who also writes the blog "TSA Out of Our Pants!," describes the use of the much-disliked scanners as "nothing but a giant fraud."

A spokeswoman for the TSA, citing the ongoing lawsuit, declined to comment on the claims noted in Corbett's brief. When specifically asked about the scanners, she said nobody was forcing anyone to fly and that there were many other modes of transportation.

Corbett isn't the only critic of the much-disliked body scanners.  Some security experts have also questioned their validity.

"There is absolutely no evidence that full-body scanners have had any effect on security, and a lot of evidence that they can't detect the sorts of explosives they were intended to detect -- the plastic explosives used by the Underwear Bomber and others," said Bruce Schneier, an internationally known security technologist and Fellow at the Berkman Center for Internet and Society at Harvard Law School.

"At this point, they are nothing more than expensive security theater," Schneier said of the $200,000 machines.

In 2010, Corbett filed a federal lawsuit asserting the scanning machines, along with full-body pat downs, were forms of unreasonable search and violated constitutional rights.

Corbett gleaned the TSA's apparent admissions after poring through 4,000 pages of documents - many of which contained classified information which the feds ordered him not to reveal - to prepare a brief that he submitted early this month to the U.S. Court of Appeals for the 11th District.

He prepared two versions of the brief. In one, sensitive material was heavily redacted by order of the federal government.

Last week, a court clerk apparently published accidentally the unredacted version to the Internet via the government's PACER service. That version was subsequently posted on numerous websites and social media outlets.

A judge immediately issued a gag order prohibiting Corbett from talking about the redacted information.

With access to the the unedited version, some readers believe they can discern what the TSA would prefer to be kept under wraps.

Among the statements Corbett obtained from various TSA "Civil Aviation Threat Assessments" and included under a section of his suit:

"As of mid-2011, terrorist threat groups present in the Homeland are not known to be actively plotting against civil aviation targets or airports; instead, their focus is on fund-raising, recruiting, and propagandizing."

Corbett said he found by reading the TSA documents that no terrorist has attempted to take an explosive onboard an airplane through a U.S. airport in 35 years; that all of the explosives brought onboard airplanes "in the administrative record" happened outside the United States; and even on a global scale, the use of explosives on airplanes is "extremely rare."

He cites a TSA analysis of hijackings in 2007 that found only seven hijacking incidents, none of which involved actual explosives; that the 9/11 hijackers were armed only with knives; and that the government concedes that it would be difficult to repeat a 9/11 incident due to hardened cockpit doors and passengers' willingness to challenge any would-be hijacker.

"Further, the government admits that there have been no attempted domestic hijackings of any kind in the 12 years since 9/11," he states in his suit.

Corbett does not address, however, whether the TSA screenings might have been a deterrent simply by their presence.

In addition to the suit, Corbett has shot a number of videos. His "How to Get Anything Through a TSA Nude Body Scanner," in which he uses a simple sewing kit to circumvent the machines, has garnered more than 2.1 million views on YouTube.

In an interview with Philly.com, Corbett said he had had several "bad encounters" with the TSA before filing the suit, "but the impetus for filing was not due to any particular incident that happened."

"I feel very strongly that the government has eroded our privacy rights during the last few decades," Corbett said. "I felt this needed to be challenged."

The machines, which were once set up to produce naked images of screened passengers, are easy to trick, Corbett said.

"They are so easy to beat," he said. "I can't get a gun through a metal detector, but I can through their scanners."

Metal detectors are much more effective at detecting weapons and dogs are more effective at sniffing out explosives, he said.

A TSA information officer said the agency provides a level of security screening required by Congress and that the TSA is always looking to enhance security procedures. "And the scanners are part of that," the officer said.

In the suit, Corbett's description of the scanners reads like a passage from a novel by William S. Burroughs.

"The nude body scanners serve to palpate every inch of skin, this time with electromagnetic radiation rather than fingers," Corbett wrote in his brief. "Every crevice, fold, and bump is turned into a picture of the traveler's nude body. It is, essentially, the high-tech version of an invasive pat-down."

But it's unlikely the TSA will give up the machines.

"They allow the TSA to find other things, drugs, primarily," Corbett said. " They get to justify their existence and their large budgets."

Understandably, the TSA has targeted Corbett for criticism.

A writer for the TSA's official blog sniped at him shortly after he posted his viral video, dismissing Corbett as "some guy" who made a "crude attempt" to beat their body scanners.

"We've never claimed it's the end all be all," said TSA blogger Bob Burns. Though Burns said the TSA has "20 levels of security," Corbett points out the TSA did not deny that the scanners could be easily fooled.

Corbett said the TSA has directed more pointed language at him. But he won't stop speaking out until the scanners are removed from all American airports.

"They said I talked like a terrorist," he said. "Anyone who dares to challenge their authority, they believe must have ill intent. But let me tell you, if I was a suicide bomber I wouldn't be taking this through the courts right now."