On September 11, 2001, al-Qaeda, an Islamist terrorist organization led by Osama bin Laden, executed a plan in which a group of (in the end) 19 men, mostly from Saudi Arabia, hijacked four passenger jets in order to crash them into the NYC World Trade Center's twin towers, the Pentagon, and possibly the Capitol Building.
Besides the unspeakable horror that this plan unleashed, it also gave birth to a conspiracy theory unlike anything the United States had seen since Pearl Harbor. 9/11 conspiracy theorists (collectively referred to as "truthers") claim that the attacks were condoned by the U.S. government, or even carried out by the government as a false flag operation, as a pretext for launching the War on Terror. More extreme variations on these theories suggest that the attacks were masterminded by an international Jewish conspiracy, or that they were carried out as part of an ongoing strategy to bring about the New World Order.
|Some dare call it|
 Claims of the conspiracy theorists
 Flight 11/175
Were explosions heard/seen in New York that suggest the WTC buildings were deliberately destroyed? This rather tedious contention, known to most as the "controlled demolition" theory, claims that the World Trade Center buildings, either WTC 7 or the entire complex, were brought down in a stealth demolition similar to the destruction of large buildings. The problems with this are, to say the least, numerous, and we'll deal with them in little bits.
 The preparations were made in secret
Rebuttal: This is pretty much completely impossible. Planned implosions require months of preparation, including tearing apart walls to place charges, removing extraneous material from the building, laying miles of carefully measured detonation cord, and the intentional damaging of support columns. Even night work would attract attention from the cleaning crew, as well as the workers who came in the next morning to find walls covered with fresh plaster.
On top of this, the WTC was bombed in 1993,[wp] meaning that there were routine checks from bomb squads, including sniffer dogs. Not only would these explosives have to be laid at night in secret, they would also somehow be able to beat animals specially trained to detect them.
 Larry Silverstein was not in the Twin Towers on 9/11
Larry Silverstein (the new leaseholder for the WTC) had been going to the Twin Towers "Windows on the World" restaurant (there were no survivors on this level) to dine and meet with his new tenants; he had been doing this straight since July 26, 2001. But on 9/11 he didn't go because he claimed his wife made a dermatologist appointment for him. Many truthers also point out that in the interview which he is asked where he was on 9/11 he appears to be showing signs of lying.
Rebuttal: It is very likely he was indeed simply going to a dermatologist appointment. Out of the thousands of people who worked at the site during the day, many dozens at any one time would have been on holiday, off sick or simply slacking on September 11th (a good half dozen well-known celebrities were involved in and avoided a potential end in the attacks). That one of these happened to be the owner isn't remarkable. There are plenty of important traders who did die in the attack — by the logic that one escaped suggests a conspiracy, the fact that many died should discredit it, right?
Also going against the idea of advanced-knowledge is that Neil D. Levin, the head of the Port Authority of New York and New Jersey (which presumably would be "in on" any conspiracy), was killed on 9/11-while dining in Windows on the World, no less. If there was advance knowledge, why was Silverstein informed while Levin wasn't?
 Silverstein's insurance "scam"
It's been repeatedly reported that Larry Silverstein had insured the Twin Towers a year earlier, and it is more than "coincidental" that this insurance covered terrorist attacks. Further, Silverstein had numerous legal disputes that aimed to increase the payout by arguing that there were two separate attacks. To a first approximation, this was successful and Silverstein managed to claim approximately $4.6 billion.
Rebuttal: What conspiracy theorists don't mention about this is that the total cost of the towers was significantly in excess of this — the insurance value was way below what it should have been. Most of the legal wrangling after the fact was also due to the insurance contracts being incomplete. The total cost of the attack would be in the region of $7 billion or more, leaving a considerable cost once the relatively measly insurance payout was claimed. With too low an insurance value and less-than-solid contracts, literally none of the insurance-based activities seem to point to the actions of people who knew exactly what was going to happen in advance. If it was an insurance scam, it was the worst ever.
We've already noted that the World Trade Center had already been bombed once before in 1993, and that several major terror plots against U.S. landmarks had been uncovered since then. In light of this, an anti-terrorism insurance policy would appear to be an entirely logical purchase.
 Bomb-sniffing dogs were removed from the building
The basic quote you see most often is:
“”Daria Coard, 37, a guard at Tower One, said the security detail had been working 12-hour shifts for the past two weeks because of numerous phone threats. But on Thursday, bomb-sniffing dogs were abruptly removed.
"Today was the first day there was not the extra security," Coard said. "We were protecting below. We had the ground covered. We didn't figure they would do it with planes. There is no way anyone could have stopped that."
|—Newsday, September 12, 2001|
Rebuttal: Note that it is extra security in response to the phone threats that was removed. The standard level of bomb-sniffing dogs was still present, and in one case, crushed when the tower collapsed. Even if all bomb dogs were still present, their presence would either be ineffective (i.e. not able to already detect explosives being planted in the pillar), or weren't able to stop a rushed-job where sufficient explosives were somehow added overnight without being detected.
 WTC 7 was demolished by order of the WTC's owner
Rebuttal: This comes primarily from two miscommunications. The first was by BBC News, which broadcast an erroneous report that WTC 7 had collapsed while the building could still be seen standing through the window of their New York studio. The second was an evacuation order ("pull it") that went out shortly before the building, badly damaged in the collapse of the main towers and on fire, collapsed of its own accord. According to the National Institute of Standards and Technology's (NIST) 2006 Federal Building and Fire Safety Investigation of the World Trade Center Disaster report, the reasons for the WTC 7 collapse include:
“”Debris from the collapse of WTC 1, which was 370 feet to the south, ignited fires on at least 10 floors in the building at its south and west faces. However, only the fires on some of the lower floors — 7 through 9 and 11 through 13 — burned out of control. These lower-floor fires — which spread and grew because the water supply to the automatic sprinkler system for these floors had failed — were similar to building fires experienced in other tall buildings. The primary and backup water supply to the sprinkler systems for the lower floors relied on the city's water supply, whose lines were damaged by the collapse of WTC 1 and WTC 2. These uncontrolled lower-floor fires eventually spread to the northeast part of WTC 7, where the building's collapse began.
... [T]he thermal expansion of building elements such as floor beams and girders, which occurred at temperatures hundreds of degrees below those typically considered in current practice for fire-resistance ratings; significant magnification of thermal expansion effects due to the long-span floors in the building; connections between structural elements that were designed to resist the vertical forces of gravity, not the thermally induced horizontal or lateral loads; and an overall structural system not designed to prevent fire-induced progressive collapse.
Although it wasn't completely obvious to the untrained eye at the time, WTC 7 had been seriously compromised by a 20-story gash in one corner facing Ground Zero, and by the time the evacuation order was given was visibly sagging. Conspiracy theorists have also tried to claim that "pull" is standard jargon within the demolition industry to fire off demolition charges within the building; demolition experts have denied this; the usual term would be "shoot it" or "blow it." "Pulling" refers to a procedure of attaching hauser cables to a building and using heavy vehicles to pull it over, something that would have been fairly easy for observers to detect. 
 The towers fell in their own footprint; if they collapsed from metal fatigue they should have been all over the place
Rebuttal: While the idea of a giant building toppling over like a felled tree is popular in fiction, in reality the structure is designed to bear its weight straight down and in no other direction; throwing a massive building severely out of equilibrium would cause it to fall almost vertically, no matter what direction the initial force was applied from.
In the case of the WTC, the upper floors detached and fell through lower undamaged sections, which can be clearly seen until they're obscured by dust and smoke. This falling mass would be too large for any one floor below it to stop or substantially redirect. NIST concluded that:
Based on observations of the collapses as they happened and hundreds of experts' analysis of the building site and materials, the NIST was able to consider and reject other possible explanations for large buildings collapsing in their own footprints. The first is the theory that damage to the WTC floor systems caused their progressive collapse, known as the "pancake theory." The second is the theory that the Twin Towers were destroyed by controlled detonation. Neither theory matches the observation that each building appeared undamaged except at its top until it collapsed. The NIST concluded that damage to perimeter support columns initiated the detachment of the floors at and above the fire and impact floors, which subsequently fell into and through the towers. The claim that a building damaged by metal fatigue cannot collapse vertically does not square with observations of the collapses as they happened, nor the conclusions of experts evaluating the effects of physical damage to and the weakening by unusually high temperatures of critical building structures. WTC 1, 2 and 7 were not the first steel-framed structures to ever collapse from fire.
In addition, the buildings did not fall onto their footprints: they left substantial debris scattered across the entire WTC complex site, damaging or destroying almost all of the surrounding buildings, mostly with large pieces of the external aluminum cladding forced outwards by the descending mass of the floors. The damage to WTC 7 was actually caused by debris from WTC 1, 370 feet away. A controlled demolition would presumably try to avoid such behavior.
 You can see flashes all over Building 7 as the demo charges fire off
Rebuttal: You can see flashing... sort of, but it isn't an explosion. What you see is window glass popping out as the floors collapse and compress the air inside. The sun is momentarily reflected in each pane of glass as it falls.
 Thermite was used to cut structural members in the buildings
Rebuttal: This is based on a few pictures of vertical beams that had been sheared off by recovery workers. Although a thermite reaction is highly exothermic, it is nearly impossible to effectively channel it sideways to cut a vertical beam, since it tends to pour straight down as it burns.
Some creative truthers have suggested the use of "thermite straps"; given that thermite is generally a powder delivered from a cone-shaped cup, it's not clear that such a device is even possible, much less practical. This was later amended to thermate, a variation which includes sulfur, and appeared when there were chemicals were found that matched what was found in the debris. However, such claims ignore the natural occurrence of these chemicals, do not match the chemical signatures that were found in the debris, and do not have corresponding traces of two major byproducts from thermate, aluminum oxide and barium nitrate.
Moreover, the thermite reaction is highly exothermic. Supposed evidence of thermite use is the presence of unreacted thermite in the WTC debris. This, however, comes as close to falsifying the hypothesis of thermite use as one can reasonably get: any place containing significant amounts of elemental aluminum and iron oxide (unreacted thermite), yet not far higher amounts of aluminum oxide and elemental iron (the reaction products), can be safely assumed to be not even close to where a thermite reaction recently occurred. This criticism has been "answered" by claiming that the unreacted "nanothermite" is indeed merely a trace residue. But this would require attaching some 100 metric tons of thermite to the WTC buildings' structure, in hundreds or even thousands of small packages, with nobody noticing. And even if that were true, the corresponding amount of reacted thermite has simply failed to turn up. Finding thermite educts yet failing to find the appropriate amount of thermite products turns the supposed "proof" of thermite use into a quite robust refutation of thermite use.
In any case, "unreacted thermite" is composed (in bulk) of elemental aluminum and iron oxide. Commercial aircraft contain enormous amounts of aluminum, and the WTC was an aluminum-clad, steel-cored building. If an airliner crashes at high speed into a large steel-frame building, causing an enormous explosion, fire, and building collapse, we can expect to find aluminum and iron oxide, as well as aluminium oxide and metallic iron, in the debris without any thermite charges being required to explain it.
A more recent truther claim is that traces of red-gray chips and iron-rich microspheres in the WTC rubble are best explained by thermite. This is held as their "smoking gun." A study of the dust from Ground Zero contradicts this: "There is no evidence of individual elemental aluminum particles of any size in the red/gray chips..." Essentially, the chips are epoxy resins.
 Explosions coming out the windows of the towers are indications of an explosive demolition
Rebuttal: What happens when you squeeze a concertina? These side-jets of air and dust were not really explosions as such but debris being expelled from the buildings as the floors pancaked on top of each other. There is a lot of air in a quarter-mile-tall office building, and when compressed it has to go somewhere.
 The "pyroclastic flows" of dust indicate that explosives must have been used
Rebuttal: A pyroclastic flow is a movement of hot gas. In the context of a volcano, it is usually hot gases containing hot dust and other chunks spreading out. In the context of WTC, these flows were claimed to be the cloud of dust that dispersed during collapse and when the towers hit the ground.
Aside from not being hot enough to qualify as a pyroclastic flow (see volcanoes and shuttle launches), most claims try linking it with the controlled demolition theory. The only thing this debris flow indicates is a fast vertical compression that caused air inside the building to push dust outward over a large area. The same flows can also be seen during controlled demolitions but usually much smaller than what happened at WTC.
It has been estimated that the total mass of sheetrock in the internal walls was on the order of 1000 tons (US). An enormous cloud of white dust is, therefore, not entirely surprising or unexplainable.
 Molten steel was found in the basement seven weeks later and jet fuel can't melt steel.
Rebuttal: There is no documented evidence of the presence of actually-melted steel at ground zero. The molten material noted in the 9/11 Commission report was "slag," not a molten metal. Most of the reports of "molten steel" found at ground zero were merely references to obviously red-hot solid steel. Even if they actually found "molten" metal, aluminum (which the planes were made out of) melts well under the temperature of jet fuel (pure aluminum melts at 660° C, jet fuel burns around 980° C going up to +2,000 °C). In addition, the mix of jet fuel, plastics, rugs, curtains etc. may burn hot enough to melt aluminum. (This can be demonstrated by placing an empty aluminum soda can on top of an ordinary campfire.)
Additionally, the melting point of steel is within the range of 1425-1540° C, well outside the temperatures recorded at Ground Zero in the weeks following the attacks. What conspiracy theorists fail to note is that steel thermally expands while it remains strong and thus fire rapidly destroys uninsulated steel structures, and steel begins to lose its structural integrity (and red hot steel itself burns in air or in the presence of steam) at well below its melting point, or 700-820° C, well within temperatures recorded at ground zero in the weeks following the attacks). Meanwhile, molten steel is not typically found at the site of buildings that have actually been demolished using "explosives" to sever columns. Also, the first law of thermodynamics prevents even the super hot molten product of thermite charges from remaining molten long after thermite ignition. Therefore, whatever molten materials were observed at ground zero in the weeks following the collapses, that molten material was not originally present and molten at the time of the collapses (it began to melt after the collapses, not before the collapses).
That all being said, a 767 Family plane can carry up to 90,000 liters of fuel in its hull. It is estimated the two planes had about 28,000 Liters left in their tanks which is spread all over the hull from the wings to the fuselage (for ballast and balance control). The crash and shredding of the plane hardware caused the fuel to ignite almost instantly. Since it was not a controlled burn it is likely to hit the highest end of the combustion scale at its core, causing simultaneous ignition of anything around that was combustible and causing severe damage to load bearing pillars.
 Hysterical do-gooders ensured there wasn't enough asbestos in the building
This theory, proposed by none other than Andrew Schlafly, holds that "Big Government," Nanny-Statism, hysterical environmentalists, lawyers and do-gooders had ensured that spray-on asbestos was not allowed in the WTC buildings, thereby ensuring they were not properly equipped to resist the fires that engulfed the structures.
Rebuttal: This is moot: any fireproofing that was there was blasted or torn off the core by the initial impact and explosion. Asbestos protection (of any kind) would've proven useless.
 The buildings were full of asbestos, and this was the least expensive way to get rid of it
Rebuttal: This contradicts the previous claim. The argument is that if Larry Silverstein had removed the asbestos from the towers in the proper fashion, it would have cost him a huge amount of money, and officially demolishing the building would have been nearly impossible under New York City laws. So when he overheard that the powers that be were plotting to crash a couple planes into his towers, like any good tycoon he sensed an opportunity (asbestos removal paid for by the government!), not a threat (the government wants to destroy my building and they expect me to be on board?).
This is one of the few bases that truthers provide as a reason to plant explosives in a building that's going to be hit by planes: the towers had to go away completely, with no chance of being rebuilt.
 The Empire State Building was hit by an airplane and survived; why not the WTC?
On July 28, 1945 a B-25 bomber,[wp] because of poor visibility, crashed into the 80th floor of the Empire State Building. Some truthers seem to think that if a skyscraper survived a similar incident the towers should also have.
Rebuttal: The two incidents were very different. Although smaller than the towers were, The Empire State Building is a much heavier building. The Empire State Building is a steel-framed structure with movement-resisting bolted or riveted connections: this means that every joint resists bending moments and wind forces and the load from any failed/ damaged columns can be redistributed, whereas the WTC's steel framed-tube configuration allowed only the exterior wall to resists bending moments due to wind. The Empire State Building's structure can redistribute loads from failed/damaged columns, but the core steel columns of the Twin Towers only supported downward loads.
The B-25 was a twin-engine World War II bomber. It was much smaller and far slower than the Boeing 767 airliners which crashed into the Twin Towers. The B-25 is estimated at 9,750 kg flying 320 kph, versus a Boeing 767-223ER (AA 11) or 767-222 (UA 175) with a mass of at least 90,000 kg flying at 750 kph (or 950 kph) respectively. Liberal estimates of the B-25 give 40 million kilojoules of kinetic energy on impact, while a conservative estimate gives AA 11 2 billion kilojoules and UA 175 3 billion kilojoules, resulting in least 50 times the kinetic energy on impact. Furthermore, the B-25 was a propeller-driven aircraft, which meant that it was powered by high-octane gasoline instead of jet fuel, and the B-25 carried way less fuel than does a modern airliner. Finally, the fire in the Empire State Building was different than in the World Trade Center and the FDNY was able to extinguish it before it got out of control.
 There was a nuke in the basement
Rebuttal: No there wasn't. None of the basic characteristics of a nuclear detonation (intense flash, thermal pulse, observable radial shockwave, emission of nuclear radiation, or electronic devices being fried by EMPs, etc.) were exhibited during the event. The physics departments of NYU, Columbia, Stuyvesant High School, and every other school in the area would have been all over that with Geiger counters, and most of Lower Manhattan would be uninhabitable for years. (Also, to put it in perspective, the 1988 PEPCON explosion in Nevada was less than a tenth of the size of the Little Boy explosion at Hiroshima in 1945, and not even half the size of the fizzled North Korean nuclear test in 2006. That'd have to be one hell of a small nuke, and it doesn't even begin to take into account that the tower collapses started from the impact sites, not the basement.)
The shockwave also would have easily registered on seismic counters all over the world that listen for nuclear testing.
 Space beams!
A theory put forward by a Dr. Judy Wood claiming that as the planes hit the towers, they were also hit by an energy weapon FROM SPAAAAACE!!! Also known for coining the term "dustification." The pseudoscientist Richard Hoagland was so enamored of this theory he went to a conference in Amsterdam (April 2011) and delivered a lecture about Judy Wood's theory for more than two hours. He did not have permission from Wood and he acknowledged her only briefly.
Wood guested on Coast to Coast AM on the thirteenth anniversary of the attack, re-iterating her contention that the towers were "dustified." Even George Noory showed a little impatience when Wood said "Well are the towers still there or aren't they?" Noory replied "Are we being silly now?"
Rebuttal: The whole theory is so absurd that another truther debunked it.
 Flight 77
 There is no conclusive video evidence that any aircraft hit the Pentagon
The one video camera on the scene that was actually trained on the site of the crash was a time-lapse camera that flipped from a vague shot of the beginning of something incoming to a full-blown explosion. 9/11 truthers have argued that without a direct image of an airplane in the security footage, it can't be proven that what hit the Pentagon was actually a plane. They back up this claim by saying that there was no plane visible in the post-crash pictures. Adherents of this theory are sometimes called "no-planers," though the term has generally come to be associated with the biggest cranks in the movement who believe no planes hit the WTC either.
Rebuttal: There were six frames from a security camera showing impact released after a FOIA request. Furthermore, there is photographic evidence of wreckage on the scene and eyewitness accounts of plane wreckage and damage consistent with a plane crash. Essentially, the problem for no-planers is that the plane did not just hit the outside of the Pentagon, but actually penetrated some distance into the structure, some of which actually collapsed on top of the plane. Numerous witnesses saw it approach, the plane's wings took out several light posts on a nearby roadway on the way in, and plane components were scattered all over the Pentagon lawn.
Also, although inconclusive (and "personal commentary") a photo was presented on a 9/11 truther website claiming that the "round" debris observed was not possibly the wheel of the alleged jetliner. However, it clearly was, albeit stripped of its outer edge.
In any case, why would anyone expect a high-res video camera to be pointed at the exact spot where the plane hit? The intrinsic improbability of such a circumstance would make it direct evidence of a conspiracy, and no self-respecting conspiracy would allow evidence of its existence to remain.
 The damage at the Pentagon is not large enough to have been caused by a passenger jet
Rebuttal: These claims rely on the remote assessment of non-specialists against the on-site investigation of experts on structural engineering. The Pentagon is a reinforced concrete building with blast-resistant windows. It was struck by an aluminum-skinned commercial aircraft that had already lost a wing before hitting the building: such an aircraft is mostly empty space, with voids in the wings for fuel and the fuselage for passengers; only the floor of the passenger compartment, the undercarriage and the engine cores are particularly solid objects. The damage is consistent with this scenario: nobody but truthers would seriously expect a cartoony plane-shaped hole–.
 If people driving near the Pentagon who apparently were witnesses of the plane actually saw it, it would have blown them off
Rebuttal: Not proved, and insignificant. (See rebuttal to the next point.)
 Other evidence suggests it was a missile that hit the Pentagon
Rebuttal: The preponderance of evidence suggests that a commercial aircraft hit the Pentagon. An aircraft is known to have gone missing, the wreckage of the same aircraft was found at the Pentagon, and the damage was what structural engineers expected from such a strike. If the alleged conspirators went to this level of effort to create the illusion that a plane had crashed into the Pentagon, why then use a missile? Using a plane would be simpler (as you already have one ready for the task), and there wouldn't be the risk of discovery.
 Flight 93
 The military would have scrambled to intercept
The US Air Force has planes that can hit Mach 3 (2100 mph) in moments. Why weren't they on the scene of the "missing" passenger jet planes?
Rebuttal: This is a charming conceit on behalf of people with a childlike faith in the US military, who cannot possibly imagine how bloated and inefficient an organization with nearly unlimited amounts of money can get. First off, the fastest combat plane in the US Air Force at the time was the Boeing/McDonnell-Douglas F-15 Eagle, it can hit Mach 2.5 tops, so wherever that Mach 3 came from is a bit of a mystery with only one unarmed high-altitude reconnaissance plane[wp] in the Air Force ever hoping to achieve that. Secondly, there were only a handful of squadrons on combat alert that day, and that doesn't mean that they are fueled up, armed, and with pilots in them (bored out of their heads). In addition, the speed of events at which the attacks happened and the often conflicting information made it far too fast to stop.
In addition, USAF keeps its eyes on US airspace outside the US, where there is ample time to scramble fighters to stop bombers from that vodka-drinking country. It then falls to the Federal Aviation Administration (FAA) and the FBI to keep their eyes on American skies (Note: Those agencies don't have planes they can scramble).
 Flight 93 was shot down and the passengers did not fight back against the hijackers
Rebuttal: There were recorded phone calls, either made from cell phones or airplane seat-back phones telling what was going on and about what was going down on the airplane. Cockpit voice recorders also picked up the sounds of fighting near the cockpit, and suggest that the hijackers crashed before reaching their destination because they knew they were in danger of being overrun. Furthermore, USAF did scramble two F-16s to intercept Flight 93. However, prior to 9/11 the Air Force did not have fighters stationed in the continental United States armed (this was a leftover from the Cold War as advanced warning systems would likely have given USAF ample time to prep fighters).
The two jets scrambled to intercept would have had no choice but to ram United 93 out of the air, which has been compared to kamikaze. This would almost certainly have been a death sentence for the pilot and would have been absolutely guaranteed to destroy the pilot's plane. The pilots returned safe and sound, their jets intact, hence United 93 could only have been brought down by the passengers who had retaken the flight.
 The debris field is too big for the size of a plane crash
Debris was found at a different community called Indian Lake, which, according to conspiracists, is six miles from Shanksville, Pennsylvania. This is true, if you follow the roads. However, debris kicked up in the air does not follow the path that Google Maps would find, but instead would take a straight line, to a community which is only about one-and-a-half miles away.
Rebuttal: Ask any crash investigator and they will will tell you that debris from a high speed steep impact can stretch for miles if an explosion occurred.
 4/29 Truth
 It was a neoconservative plot
- George W. Bush did it
- Dick Cheney did it
- Donald Rumsfeld did it
- Richard Perle did it
- Paul Wolfowitz did it
Rebuttal: The "new Pearl Harbor" quote was in reference to modernizing the military and had nothing to do with declaring a war. It stated that progress with modernization would be slow barring an event causing a seismic political shift, it wasn't a statement of intention to create one.
- Elvis Presley pretending to be a janitor did it.
- Goats did it
- I didn't do it
- Anonymous readers of this site did it
As with any claim, the burden of proof lies upon the claimant. Apart from the one about me, because I definitely didn't do it.
 Powerful money/Bush family/military-industrial conspirers did it, all of whom needed a new war in the Middle East for various commercial reasons (oil, arm sales, real estate, precious bodily fluids etc.)
Rebuttal: While it could easily be said that "they" used 9/11 to create an unrelated Iraq War, they did not blame the Iraqis, but al-Qaeda, which isn't really as convenient if you want to declare war with Iraq and not lose some friends. To quote Bill Maher, "[That Bush had prior knowledge of the 9/11 attacks] is an absurd statement, because it contains the words Bush and knowledge."
 It was carried out by Mossad to galvanize US support for Israel and destroy their enemies
Rebuttal: The story of Mossad allegedly telling Jews to stay home the day of the attack, or that no Jews died in the attack, both of which are false, brought this one forward (the most common of these claims is that 4,000 Jews were warned to stay home). However, as Bush was already one of the strongest supporters Israel has ever had, it is questionable as to why they'd need more of his support.
The idea that the Jews were forewarned may originate in the fact that 9/11 happened to fall at the end of the month of Elul, during the days leading up to Rosh Hashanah, when observant Jews would have additional prayers at their morning prayer services and therefore would likely be late to work. However, given that there were several Orthodox minyanim (prayer groups) organized within the WTC, it is unclear how many, if any, Jews were away from the towers due to prayer services. Then again, if Mossad had wanted to destroy the towers when there were no Jews in them, they could simply have waited a few days until Rosh Hashanah or Yom Kippur, when practically no Jews would have been at work.
 A former CIA operative confesses
In 2010, Susan Lindauer self-published a book titled Extreme Prejudice: The Terrifying Story of the Patriot Act and the Cover-Ups of 9/11 and Iraq. In this book, she claims to have been working with the CIA and DIA for years.
Rebuttal: Sources like Wikipedia do not make any mention of these claims outside of the section dedicated to the book. Lindauer may not be sane to begin with, as she was deemed "unfit to stand trial" after refusing to take medicine to aid with a mental illness. This position was reaffirmed two years later.
 Bush allowed 9/11 to happen
Another version of the conspiracy theory is that although 9/11 wasn't planned or carried out by the US government, Bush was aware that 9/11 was going to happen and did nothing to prevent it. The most high profile proponent of this theory is former counter terrorism czar Richard Clarke, who says the Bush administration ignored warnings of a likely attack from Al-Qaeda. This was however to suggest (with considerable validity) that the Bush administration was incompetent in its pre-9/11 security preparations rather than to accuse them of intentionally letting the attack happen. 
Rebuttal: It is known that Condi received a memo entitled "Bin Ladin determined to attack inside the U.S." on August 6, 2001, but this memo discussed the threat in a general way and made no mention of the specific individuals who carried out the 9/11 attacks. Nevertheless, the existence of this memo, Bush's reported flippant response "you've covered your ass, now" and the fact that it was not declassified until years later have contributed to the aura of foreknowledge and coverup.
 Freemasons/Knights Templar/Zionists/Skull and Bones/"your secret fraternal society dedicated to world domination here" did it
This "argument" relies, primarily, on interpreting architecture and symbolism within US culture as indicating that a conspiracy was openly declared for decades and part of some unknown secret plot by an illustrious and secretive elite society that has been alleged to be anything from protean space lizards who have been ruling the world for centuries to a cadre of rich guys who hang out in the woods every summer. These often include references to the Twin Towers as being constructed as symbolic of Solomon's twin pillars, Boaz and Jachin (which is an important symbol in Freemasonry as well as other esoteric literature such as tarot cards). Various premonitory events such as The Simpsons featuring a picture of the twin towers with the number 9 next to it or The Dude in The Big Lebowski signing "September 11th" on a check are cited to "prove" that someone has been secretly dropping clues for decades that 9/11 was going to happen. Unlike other conspiracy theories, these theorists do not typically reference the actual events surrounding 9/11, but instead point out symbolic indications claiming that it was "foretold."
Rebuttal: As with all forms of pareidolia and confirmation bias pointing out examples where the Twin Towers show up is not evidence given that the Twin Towers were, in and of themselves, highly recognizable buildings, and, therefore likely to be included in multiple forms of literature, especially when referencing New York City. Additionally, it seems highly unlikely that anyone plotting mass murder on the scale witnessed during the WTC attacks is going to tell anyone about it in advance.
 Building six is missing its interior
A claim made in 2013 is that building six is missing its interior, but its walls are intact. 
 A number of al-Qaeda members conspired to hijack some planes and attack some buildings
...okay, we'll give you that one.
 Loose Change
An Internet phenomenon, Loose Change is a "work" was a huge hit on Google Video and beyond, and is one of the rare examples of an amateur Internet film to have made the leap to the mainstream media, going on to be broadcast in the UK. It advances many of the most popular conspiracy theories about 9/11.
 False false flag operations
Truthers like to cite false flag operations that never actually happened or weren't actually false flags as "precedent" for the 9/11 conspiracy, though even citing real false flag operations would not constitute evidence that 9/11 were a false flag:
- Hitler burned the Reichstag as a false flag operation to grab power!
- Rebuttal: Historical consensus is that the communist dissident charged with setting the fire was the one who did it. There is some debate over whether he acted alone, but little evidence to show that the Nazis were involved in any way. Even if it were true, though, one guy setting an empty building on fire is hardly analagous to a 9/11 conspiracy.
- FDR did Pearl Harbor!
- Rebuttal: Another conspiracy theory. See the Pearl Harbor conspiracy theory page for a full debunking.
- Operation Northwood was a plan for a false flag attack.
- Rebuttal: This made it into the second cut of Loose Change, which alleges that a plan to blow up drone planes as part of a false flag operation to justify the invasion of Cuba is a precedent for a 9/11 false flag. This plan was proposed by a few members of JFK's Department of Defense. JFK and Secretary of Defense Robert McNamara dismissed it as batshit crazy. If anything, this is a precedent for the president discounting such false flags.
- LBJ did the Gulf of Tonkin!
- Rebuttal: There were two Gulf of Tonkin incidents involving the USS Maddox in 1964. In the first, the Maddox did engage with North Vietnamese torpedo ships. In the second, the Maddox mistakenly reported itself as being under attack. This incident was massively exaggerated by LBJ to justify the escalation of the Vietnam War, but it wasn't a false flag operation.
 Problems with the "Bush did it!" theory
“”Within eight months of taking office, President Bush planned and executed the largest terrorist attack on U.S. soil with the full cooperation (and unbroken silence) of the U.S. military, intelligence community, and airline industry. Eight months.
|—Mike Sawyer on what 9/11 truthers actually believe|
As aformentioned, the biggest problem is that for the Bush administration to enact such an abhorrent plot and keep it a secret would seem to require a level of competence they never displayed at anything else. While there is some evidence that intelligence regarding the attack was ignored, that does not mean it was a nefarious plot. As Heinlein said, "You have attributed conditions to villainy that simply result from stupidity."
The second problem is that if BushCo did stage the 9/11 attack, their failure to place the blame directly on Saddam Hussein's regime is rather baffling, since their alleged main "use" of 9/11 was to force the US into war with Iraq.
 Why use explosives?
Apart from all the problems regarding means and opportunity to plant hidden explosives in the buildings, there's also the question of the motivation for those particular means. Presumably, a "hypothetical" situation in which jetliners hit the buildings and no bombs were involved (i.e., the real situation) would have caused quite a lot of damage, killing many people and searing into the minds of Americans an image of two buildings attacked by terrorists. So why would the conspirators bother with bombs in addition to jetliners? (Alternatively: why bother with jetliners in addition to bombs?)
Truther answers vary. Only a few of their arguments actually suggest any relevant differences between the known scenario and what they imply would have been observed in a bomb-free one. One difference is that the towers fell straight down into their own footprints (as opposed to sideways, or just the tops flying off by themselves). Another is that their speeds approached free-fall. In short, we are supposed to believe that the conspirators would not have accomplished their goals without the buildings falling quickly and straight down. (Stupid gravity.)
This point does not apply to non-controlled-demolition conspiracies, but the CD hypothesis has managed to dominate to the point of being synonymous with trutherdom. Why? Perhaps because controlled demolition offers more hope of an un-dismissible smoking gun than the mere LIHOP argument ever could. (Any scenario where the buildings came down per the mainstream view is one that could only be exposed by a paper trail, confessions, etc, but physical evidence like bombs would seal the deal.) Ironically, though, it is almost the least plausible of the theories (though space-beams and hologram-planes show us that one can always find a wealthier stash of crazy somewhere else).
Of course, the "Why?" problem is not an ironclad argument even if it has no answer, because (hypothetically) sufficient evidence in favor of bombs would confirm that bombs indeed had been planted. Say, if C-SPAN captured footage of a famously-sane Senator Jon Doe suddenly meowing like a cat, the fact that no one can provide a rational reason for his doing so would not somehow disprove the assertion that Smith meowed. Likewise, maybe the conspirators just like planting bombs.
In fact, maybe the purpose of the bombs was to draw in the conspiracy-theory crowd like moths to a flame: any subsequent "truth movement" would be unable to resist making themselves look ridiculous by constantly talking about something as absurd as redundant explosives! As phrased by a character in a truther-parodying dialogue in LessWrong which satirically suggests that controlled demolition ideas are in fact an instance of "disinformation" by the real conspiracy: "I don't suppose we actually planted some explosives, just to make sure...?"
23 Sep 2010: "Delegates from the US and European countries walked out of the UN's General Assembly hall during Mahmoud Ahmadinejad's speech when the Iranian president claimed 'most nations' believed the US government was behind the September 11 attacks."
 Common themes in truther thinking
A freakishly large number of truthers are shamelessly anti-Semitic, blaming in various members US neoconservatives (come on, people), property owner Larry Silverstein, and the Mossad for planning/covering up the attack. Many truthers also seem to be of the opinion that a group of Ay-rabs couldn't have planned an operation this complex, a slightly (but only slightly) more subtly racist attitude remniscent of Erich von Däniken.
Technological illiteracy is a frequent theme as well — the invention of fanciful devices such as "thermite straps" to cut vertical girders for example (thermite is very hard to direct and usually burns straight down), "quiet" explosives, very-low-yield nuclear weapons, and even undetectable holographic projectors (favored by some of the no-planers) all figure into theories put forth by truthers. Outright lying is not unusual as well; for example, claims of no plane parts on the lawn of the Pentagon were directly refuted by eyewitnesses.
Truthers also seem to have a thing for digging around in the statistical noise, misinterpreting photo artifacts and other random bits of data and even taking operational jargon (such as the infamous "pull it" command that was used to order the evacuation of WTC 7) out of context, while avoiding things like the fact that steel doesn't have to melt to bend, that office fires can be much hotter than just a kerosene fire, or the fact that there was a 20-story gash in the side of WTC 7 after the tower collapses that seriously compromised its structural integrity. In fact, the entire truther thought process is very much akin to quote mining. Who'da thunk.
At the conservative end of the truther spectrum are LIHOPers (short for "Let It Happen On Purpose," in contrast to MIHOPers for "Made It Happen On Purpose") who believe US intelligence agencies had data on the coming attacks prior to September 11th, 2001, which the administration willfully ignored, but whose direct involvement was limited to (at very most) diverting defenses that might have interfered with the attack. Still dumb. The least indulgent of the truthers speculate that the 9/11 attacks were planned and carried out by Osama Bin Laden, disgruntled associate of the Saudi Royal family, and a cadre of veteran mujahideen, and not a lone, nondescript terrorist who single-handedly hijacked and piloted all four planes to their targets.
A small but prolific number of truthers even go so far as to claim the planes were holographic.
 See also
- Cognitive infiltration
- Journal of 9/11 Studies
- Pilots for 9/11 Truth
- Project for a New American Century
- Judy Wood
- Point refuted a thousand times
- Pearl Harbor conspiracy theory
- Alex Jones
- Mark Dice
- Cynthia McKinney
- David Icke
- David Ray Griffin
- Ed Asner
- Jeff Rense
- Laura Knight Jadczyk
- Lyndon LaRouche
- Mahmoud Ahmadinejad
- Mike Adams
- Mike Stanfill
- Nico Haupt
- Texe Marrs
- Yukihisa Fujita
- Luke Rudkowski, and everyone in his activist collective We Are Change
- Truth News Australia
- David J. Stewart of Jesus Is Savior
- Adam Kokesh
- Jesse Ventura
- James H. Fetzer
- Screw Loose Change blog
- NIST reports
- Debunking the 9/11 Myths: Special Report, Popular Mechanics' well-regarded and very thorough article from March 2005 debunking conspiracy theorists' claims. (This was later expanded into a book called Debunking 9/11 Myths: Why Conspiracy Theories Can't Stand Up to the Facts.)
- Published Scientific Research on the Physics of the World Trade Center Airplane Impacts
- Debunking 9/11 Conspiracy Theories
- 9/11 Science and Conspiracy, National Geographic special
- Unraveling Anti-Semitic 9/11 Conspiracy Theories, Anti-Defamation League
- Skeptic's Dictionary on 9/11 conspiracy theories
- Was 9/11 an Inside Job?, Cracked
- September 11th Conspiracies - What Do We Know?
- First-Responder Eyewitness Accounts of the Planes That Hit the WTC
- The Onion Predicted al-Qaeda's Frustration with Ridiculous Truthers
- Thomas W. Eagar and Christopher Musso. Why Did the World Trade Center Collapse? Science, Engineering, and Speculation. JOM, 53 (12) (2001), pp. 8-11.
- S.W. Banovic et al. The Role of Metallurgy in the NIST Investigation of the World Trade Center Towers Collapse. JOM, Vol. 59, No.11 (2002), p. 22-30
- You Can’t Handle the Truthiness: A Night Out with the 9/11 Truth Community, Skeptical Inquirer
- ↑ Larry Silverstein On Getting Hit By a Car, World Trade Center Timetable, New York Observer
- ↑ "Lucky Larry Silverstein and his Jewboys just happened not to go to work that day"
- ↑ 10 Famous People who Avoided Death on 9/11
- ↑ Neil Levin, Executive Director Of Bistate Port Authority, 46, The New York Times
- ↑ Windfall, 9/11 Myths
- ↑ 9/11/01: Heightened security alert had just been lifted, Newsday
- ↑ Tribute To Sirius, K9 Bomb Detection Dog with the the NY/NJ Port Authority Police Department
- ↑ Early report of WTC 7 collapse by BBC (Appears they got it from an incorrect Reuters wire.)
- ↑ Questions and Answers about the NIST WTC 7 Investigation, NIST
- ↑ Pictures of damage to WTC 7 and "pull it" explanation at Debunking 9/11 and this video showing the penthouse collapse and uneven implosion that is not characteristic of a controlled demolition.
- ↑ 11.0 11.1 Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Answers to Frequently Asked Questions, NIST
- ↑ First time in history, Debunking 9/11
- ↑ Something would have to hold the burning thermite up — without itself melting or shattering at temperatures in excess of 4000 K — for it to remain in any one place on a vertical surface. Such highly refractory materials exist, but they are quite expensive and the procurement of large numbers of unusually-shaped items made from them would inevitably have been remarked upon.
- ↑ Large aircraft tend to contain sizable quantities of aluminum, and aluminum is a reactive metal which forms an oxide coating in air to prevent further corrosion. In addition, the cladding of the two main WTC towers was aluminum. Not finding aluminum oxide in the wreckage would be somewhat more surprising, given it would require an enormous amount of already present material to have vanished.
- ↑ 9/11 Debunked: Thermate Chemical Signatures Disproven
- ↑ Under the unrealistic assumption of 100% packing density, this would mean about 24 cubic meters of thermite; including packaging, this would approximately fill up a 20' shipping container. But for proper reaction, thermite cannot be a solidly-packed block; it has to be a fairly loose powder, meaning that the actual volume would be about twice as high. See Debunking 9/11 for the math.
- ↑ Analysis of Red/Gray Chips in WTC Dust, American Academy of Forensic Science
- ↑ Jet Fuel summary
- ↑ Performance of JP-8 Unified Fuel in a Small Bore Indirect Injection Diesel Engine for APU Applications, SAE International
- ↑ Melting temperature of some common metals and alloys
- ↑ "Did Flawed Science and Litigation Help Bring Down the World Trade Center?"
- ↑ "B52 Bomber Crashes Into The Empire State Building"
- ↑ B-25 Empire State Building Collision
- ↑ Subcritical "suitcase" nukes may exist, though the facts on the matter aren't well known.
- ↑ Oh. Play it cool. Play it cool. Here come the space cops.
- ↑ The audio of Hoagland's Amsterdam performance has since been deleted, but the lecture info can be found on this crazy site.
- ↑ James Gourley's critique of Judy Wood's Space Beam paper
- ↑ See conspiracy theorist Eric Salter's "A Critical Review of WTC 'No Plane' Theories" for an overview of these theories. (Again, some truther material is too nuts even for fellow conspiracy theorists.)
- ↑ Watch the upper right corner at 0:24.
- ↑ Debunking the 9/11 Myths: Special Report - Flight 77 Debris, Popular Mechanics
- ↑ Debunking the 9/11 Myths: Special Report - Big Plane, Small Holes, Popular Mechanics
- ↑ Gates Concerned over Bloat in US Military Hierarchy in Europe, Atlantic Council
- ↑ F-15 Technical Specs, Boeing
- ↑ The First 109 Minutes: 9/11 and the U.S. Air Force, Air Force Historical Studies Office
- ↑ The 'chilling' 9/11 audio tapes: 5 takeaways, The Week
- ↑ Flight 93 Hijack Transcript, The Smoking Gun
- ↑ F-16 pilot was ready to give her life on Sept. 11, Washington Post
- ↑ Indian Lake: Plane shot down?
- ↑ Tanker fire destroys part of MacArthur Maze / 2 freeways closed near Bay Bridge, San Francisco Chronicle
- ↑ 4/29 Truth website
- ↑ "Rebuilding America's Defenses: Strategy, Forces and Resources For a New Century", PNAC, page 51
- ↑ Absent without Leave, Snopes
- ↑ Woman Accused of Iraq Ties Is Ruled Unfit for Trial Again, The New York Times
- ↑ "9/11: allowed to happen, given technical assistance to make sure it happened, but some claims of complicity are not true"
- ↑ http://www.democracynow.org/blog/2014/5/28/former_counterterrorism_czar_richard_clarke_bush
- ↑ White House releases bin Laden memo, CNN
- ↑ Dark Secrets Inside the Bohemian Grove!
- ↑ Freemasonry: The Pillars of Solomon's Temple, MIT
- ↑ So what do you think the wad of cash stands for?
- ↑ Damn, 41 was monotone.
- ↑ http://www.youtube.com/watch?v=509xQgcoMN8 The arrogance of the guy in this video is infuriating.
- ↑ What I Learned from 9/11 Conspiracy Theories
- ↑ JREF tries to unravel the bullshit.
- ↑ The 9/11 Meta-Truther Conspiracy Theory
- ↑ Mahmoud Ahmadinejad's 9/11 claims cause UN walkout, The Guardian
- ↑ In one case, a truther showed a picture where he had apparently mistaken speedboats in the Hudson River for missile contrails.
- ↑ Both are completely different the IHOPers, who recognize that "pancaking" is a normal and expected result of skyscraper collapse.
- ↑ http://www.youtube.com/watch?v=yHpfK8hdOjY