It may have been set up before the event since seizing of surveillance camera videos within minutes of the crash. It is extremely unlikely that the conspirators who allowed (and assisted) 9/11 would not have taken care to create misdirecting hoaxes before the "attack," since they are very aware that large segments of the population would have suspicions about the events and therefore they would "need" to disrupt skeptical inquiry with red herrings, hoaxes, false dichotomies, etc.
This hoax is based on misrepresentation of photos taken shortly after the crash, ignoring of physical evidence and documented reports from hundreds of eyewitnesses who saw the plane. There is NO credible, verifiable evidence in support of ANY of the many and varied "theories" pretending that a plane did not crash into the Pentagon, and therefore, 9/11 was an inside job.
It was first floated in early October 2001 by French author Thierry Meyssan and US War Secretary Donald Rumsfeld. Monsieur Meyssan started a webpage that suggested a plane did not hit the Pentagon on October 7, and Rumsfeld gave an interview to Parade magazine on October 12 where he said a "missile" hit the Pentagon. That "missile" quote was then used by many no plane advocates as part of the campaign to draw attention to this claim. Meyssan went on to create the "Hunt the Boeing" website and then published two books "The Horrifying Fraud" (published in English as "9/11 The Big Lie") and Pentagate. These books have been translated into a total of 28 languages, which ensures that they are the dominant version of the claim suggesting complicity or conspiracy that is seen around the world.
On September 4, 2004, two months before the pseudo Presidential election, Parade magazine claimed that this quote was a mis-statement and the sole source for the no plane hoaxes, thus dismissing 9/11 "truth" to an audience of millions of voters.
The biggest claim for the no plane hoax is that the "hole" in the facade of the Pentagon was supposedly too small to have been created by a 757. Many of these claims state that photos taken during the half hour between the crash and the collapse of that part of the building show a hole merely 16 to 18 feet across. However, those photos have most of the damage obscured by firefighting foam and smoke -- the full hole was about 90 feet wide, and additional damage (from the wingtips) is visible for tens of feet beyond the hole. The impact on the outside of the building was the size and shape of the cross-section of a 757.
Perhaps the most intriguing claim from those who cling to the "no plane" claim is the fact that the Pentagon is hiding footage from the video surveillance cameras that filmed the event constitutes evidence that something other than Flight 77 hit the building. This suppression of evidence shows foreknowledge (since FBI agents who seized the film were immediately able to grab the videos), but not "no plane." Hotel workers who watched "their" video before it was seized saw the plane. And the hundreds of commuters and other bystanders who were in the area also saw the plane. The video is probably being withheld in a form of "reverse psychology" to get the skeptics to think the Pentagon is hiding something when they are not, which is needed to keep this hoax alive. Some 9/11 activists who disbelieve the "no plane" stuff think the Pentagon is planning to release "newly discovered" video of the plane hitting the building to discredit 9/11 truth, but it is more likely that they are enjoying the spectacle of the activists discrediting themselves and 9/11 complicity in general. More important, they understand that if the "no plane" claims are extinguished, most of those focused on the "Pentagate" will shift their attention toward real evidence of complicity that the "no plane" stuff distracts from.
The eyewitnesses who had a good view of the event are unified in their reporting -- they saw a large, twin engine jet. Some had better views than others, some saw the crash, some had the final moment obscured from their vantage point. Some were stuck in traffic on nearby roads, others were outside. Some were military officials, others include cab drivers, ordinary commuters and even a Unitarian minister (a cross section of people normally found in northern Virginia during rush hour). Some hoaxers claim that the eyewitnesses are not reliable, and the "physical evidence" should be used instead -- except the physical evidence shows that Flight 77 definitely hit the Pentagon.
Hundreds (if not more) people saw the plane, and hundreds more participated in the cleanup and saw plane debris and bodies of the passengers. It is ridiculous to think that everyone in the vicinity (including the rush hour traffic) was somehow an agent or dupe of the "inside job" conspirators -- that would have expanded the needed size of the conspiracy to absurd levels, and the insinuation has helped ensure that the eyewitnesses, their families, friends, co-workers, etc. think that 9/11 skeptics are rude, insulting and generally making up nonsense. Cui bono? Who benefits?
Newsweek reported a few weeks after 9/11 that the "black boxes" from the plane were found, and that data would indicate how the plane was steered in its final moments in an incredible spiral dive into the nearly empty, recently reconstructed and strengthened sector of the Pentagon. The alleged hijacker, Mr. Hani Hanjour, flunked out of flight school and clearly did not have the skills to perform that maneuver. The fact that the plane flew around the Pentagon, past Donald Rumsfeld's office, past the National Military Command Center, and struck the least populated part suggests that whoever was at the controls wanted to ensure the minimal level of casualties. Would a "terrorist" have chosen to fly this way? Even an expert pilot would have had a hard time doing this. This is strong circumstantial evidence for remote control technology. Proving its use is probably impossible, but the technology is commercially available.This suggests that remote control technology of some sort was actually used to hijack the plane, and that the role of the "hijackers" may merely have been that of patsies. The black boxes would confirm or refute this theory, but most 9/11 "conspiracy" investigators have fixated on the fleeting hope that the surveillance videos would be released (which would merely prove the obvious) while ignoring the hidden data that could actually prove something.
The "no plane" hoax discredited claims of complicity inside the Beltway among the general public and the political and military elites. Washington, DC voted 90% against Bush in 2004, and Arlington County (where the Pentagon is located) is the most Democratic constituency in the Commonwealth of Virginia. (The Republicans in the DC area are more concentrated in Fairfax County and other outer suburbs, especially those outside the Capitol Beltway.)
This hoax created a false dichotomy between "no plane" and "no complicity" when neither is true.
It is not a coincidence that many supporters of the official "surprise attack" story focus exclusively on the "no plane" theories when smearing 9/11 skeptics. The "no plane at the Pentagon" has been the most successful disinformation meme used against the 9/11 truth movement, which distracts from the fact the Pentagon was hit in the mostly empty part, why the Air Force did not defend its own headquarters and the roles of the multiple war games run by the military and intelligence agencies that morning.