The issue of whether anyone outside al-Qaeda was aware that the attacks were going to take place has been a subject of some theories. Among the theories are: whether the Bush Administration or military knew about the plan of using planes as missiles; what the intelligence agencies knew about al-Qaeda activities inside the United States; whether the put options placed on United Airlines and American Airlines, and other trades considered questionable by theorists, indicate foreknowledge; whether there were warnings from foreign countries that were specific enough to have warranted action; whether there was any intelligence information gathered about imminent al-Qaeda attacks and whether it was specific enough to have warranted action; whether the alleged hijackers were under surveillance prior to the attacks and, if so, to what extent; and whether agents of the Mossad or the Pakistani Inter-Services Intelligence were aware that the attacks were going to take place.
It has been claimed that action or inaction by U.S. officials with foreknowledge was intended to ensure that the attacks took place successfully. For example, Michael Meacher, former British environment minister and member of Tony Blair's Cabinet till June 2003, was widely criticized for claiming that America knowingly failed to prevent the attacks. Meacher had in March voted for the Iraq war, and had voted against an investigation into it afterward. On the war with Iraq, Mr. Meacher is among those who feels he and others in government were misled.
Many 9/11 theories claiming government involvement allege that the US air defense system, NORAD, was deliberately stood down or rendered ineffective. This claim originates from the 9/11 Commission Report account of the actions taken by the Federal Aviation Administration (FAA), NORAD and other military personnel. Some note that "FAA standard procedures for NORAD interception of off course or ceased responding aircraft" were activated on 129 occasions in the year 2000 and on 67 occasions in the period from September 2000 to June 2001 but failed to do so on 9/11.
Although the military first learned of the hijacking of Flight 11 from Boston Center at 8:40, just 6 minutes before its impact, it was able to scramble two F-15 fighter jets from the 102nd Fighter Wing from Otis Air National Guard Base just 12 minutes later at 8:52, six minutes after Flight 11 crashed into the North Tower of the World Trade Center. However, the 33 minute flight time didn't allow them to reach Manhattan until 9:25, 22 minutes after the crash of Flight 175 into the South Tower. One of the pilots later commented, "As we're climbing out, we go supersonic on the way, which is kind of nonstandard for us. And, and Nasty even called me on the, radio and said, Duff, you're super. I said yeah, I know. You know, don't worry about it. ... I just wanted to get there quickly."
Some theorists suggest that the war games being conducted on September 11 were deliberately planned to coincide with the attacks to create confusion.[unreliable source?] United States Representative Cynthia McKinney, former head of the Strategic Defense Initiative Dr. Robert M. Bowman, economist Michel Chossudovsky, and publisher/editor Michael Ruppert of From the Wilderness are a few of the individuals who have questioned these exercises.
"For more than two years after the attacks, officials with NORAD and the FAA provided inaccurate information about the response to the hijackings in testimony and media appearances... Some staff members and commissioners of the Sept. 11 panel concluded that the Pentagon's initial account of how it reacted to the 2001 terrorist attacks may have been part of a deliberate effort to mislead the commission and the public... Suspicion of wrongdoing ran so deep that the 10-member commission, in a secret meeting at the end of its tenure in summer 2004, debated referring the matter to the Justice Department for criminal investigation. In the end, the panel agreed to a compromise, turning over the allegations to the inspectors general for the Defense and Transportation departments, who can make criminal referrals if they believe they are warranted".
Since the 9/11 Commission places the primary blame on communication failures within the FAA, Prof. David Ray Griffin, who has written several books alleging that the 9/11 conspiracy was considerably larger than the government claims, has questioned why the US military would lie to cover up the mistakes made by that agency.
There were a number of war games and military exercises taking place during the attacks, including Northern Vigilance, a NORAD operation which involved deploying fighter aircraft to locations in Alaska and northern Canada to respond to a war game being conducted by Russia; Global Guardian, an annual command-level exercise organized by United States Strategic Command in cooperation with Space Command and NORAD; and Vigilant Guardian, a semiannual NORAD Command Post Exercise (CPX) (meaning it is conducted in offices and with computers, but without actual planes in the air) involving all NORAD command levels in which one scenario being run on September 11 was a simulated hijacking. Additionally, a National Reconnaissance Office drill was being conducted on September 11 in which the event of a small aircraft crashing into one of the towers of the agency's headquarters, was to be simulated, and the Office of Emergency Management were preparing for Operation Tripod, a bioterrorism exercise due to take place on September 12.
Members of the 9/11 Truth Movement question whether the story that such an array of war games and exercises were due to take place on that day by coincidence, is plausible.[unreliable source?] Jim Hoffman and Michael Ruppert, among others, have suggested that the war games may have been specifically organised to coincide with the attacks, in order to help disable the air defence system. Webster Tarpley, in his book 9/11 Synthetic Terror: Made in USA (ISBN 978-0930852313) claims that the war games were the "perfect cover for conducting the actual live fly components of 9/11 through a largely non-witting military bureaucracy. Under the cover of this confusion, the most palpably subversive actions could be made to appear in the harmless and even beneficial guise of a drill."
In testimony before the 9/11 Commission, Secretary of Transportation Norman Mineta said that he was not present when the order was given to shoot down the airplanes. He stated that he became aware of the order when he entered the Presidential Emergency Operation Command in the bunker underneath the White House where Dick Cheney was in command. He describes the following exchange, between Cheney and a "young man", as taking place sometime between him entering the bunker and the time the Pentagon was hit at 9:37.
There was a young man who had come in and said to the vice president, "The plane is 50 miles out. The plane is 30 miles out." And when it got down to, "The plane is 10 miles out," the young man also said to the vice president, "Do the orders still stand?" And the vice president turned and whipped his neck around and said, "Of course the orders still stand. Have you heard anything to the contrary?
Mineta did not know at the time what the orders referred to, and he learned only later that 'shoot down orders' had been given that day. However, it has been suggested that the orders spoken of could have been an order not to shoot down the approaching plane. This theory is based on an interpretation of the young man's question as an expression of his surprise about the order. Therefore, because shooting down the approaching plane would be the accepted action, the unusual nature of an order not to shoot down the plane would explain the young man's putative disbelief. . Although Mineta later clarified that he believed the order being discussed was indeed a shoot down order, the 9/11 Commission found that "A shootdown authorization was not communicated to the NORAD air defense sector until 28 minutes after United 93 had crashed in Pennsylvania". 
World Trade Center collapse
The controlled demolition hypothesis states that the collapse of the World Trade Center was due to the use of explosives. It plays a central role in the 9/11 conspiracy theories that assert that the US government is responsible for the attacks. Dr. Steven E. Jones, formerly of BYU, suggests that the official explanation that fire and debris induced the collapse of WTC 7 is false.
The Federal Emergency Management Agency Report of 2002 and the later National Institute of Standards and Technology report of 2005 regarding the reconstruction of the collapse events of the Twin Towers and Seven World Trade Center both contradict the controlled demolition hypothesis. According to a BBC the final NIST report on the collapse of building 7 to be released in the summer of 2008 will conclude that its collapse was caused by ordinary fires in burning for hours caused by a combination of the buildings unusual design, its location as well lack of water available to firefighters as well as their prioritizing saving lives. Specifically, these reports do not mention any evidence that suggests that pre-positioned explosive charges caused the collapse of buildings 2 WTC, 1 WTC and then 7 WTC. However, the NIST report has suffered a degree of criticism for its lack of physical evidence and has been called upon to produce computer visualisations to rectify this problem.
Some contend that a commercial airliner did not crash into the Pentagon; this position is debated within the Truth Movement, many of whom believe that AA Flight 77 did crash there, but that it was allowed to do so via an effective stand down of the military. Claims that the Pentagon was hit by something other than the Boeing 757 of Flight 77 have been raised, based on photographs taken after the attack, in which there appears to be a lack of expected debris or damage in and around the impact area, along with the FBI seizure and refusal to release nearby security camera footage which, it is assumed, would have captured the attack on video. The first proponent of the "No Boeing" theory was Thierry Meyssan through his book 9/11: The Big Lie and website Hunt the Boeing! His claims have been further popularized by the Internet videos Loose Change and "911 In Plane Site".
On March 8, 2002 five video frames captured by a security camera at the Pentagon were leaked. Only the first frame preceded the impact: this frame shows what may be an object heading for the Pentagon. On May 16, 2006, the security camera footage was released as part of a Judicial Watch Freedom of Information Act request. However, due to a low number of frames per second, the videos are also inconclusive, thus keeping the "No Boeing" theory alive. Security camera footage from a nearby Citgo gas station, from a local Doubletree Hotel, and from the Virginia Department of Transportation, was swiftly confiscated by the FBI. The footage from both the gas station and the hotel were later released following successful FOIA Requests, but neither captured the impact.
Additional photographs were released in 2006 after the Zacarias Moussaoui trial and several FOIA requests. Some show large aircraft parts and human remains, but no content that could prove the location is the Pentagon at the correct time.
In an interview for Parade magazine on October 12, 2001, Defense Secretary Donald Rumsfeld apparently referred to "the missile to damage [the Pentagon]". Some have interpreted this as a faux pas admission that it was not Flight 77 that hit the building. Others have suggested that the word may have been carefully chosen disinformation, designed to "trap 9/11 skeptics," citing this as the real reason why photographs and video footage have not been forthcoming.[unreliable source?] Parade magazine subsequently stated that this interpretation of Rumsfeld's words was a misunderstanding caused by a transcription error. Jim Hoffman states:
"Experts at psychological operations, the perpetrators could have anticipated that skeptics would divide into two groups: those persuaded by eyewitness evidence that a 757 had crashed, and those persuaded by physical evidence that one had not. The ongoing controversy could then be exploited by the perpetrators to several ends: 1) to keep the skeptics divided, 2) to divert skeptics' resources from other more productive lines of inquiry and 3) to provide a bizarre-sounding theory with which to tar the entire 9/11 Truth Movement."
Jim Hoffman and other members have produced essays examining the "No Boeing" claims and have concluded that Flight 77 did hit the Pentagon. Several researchers have argued that the wings would cause less damage than the plane's main body, that photographs of large amounts of wreckage and debris matching a 757 have become available, that the appearance of the size of the hole is typically misrepresented; and that the actual fuselage diameter of 12 feet is a much more relevant dimension for the deepest parts of the hole than the overall 44-foot height of the 757's tail. They also emphasize reports from numerous eyewitnesses, including commuters on nearby roads, nearby apartment buildings, and other surrounding locations. Many witnesses saw the aircraft close up as it approached the Pentagon and described it as an American Airlines Boeing 757.
United Airlines Flight 93 crashed in an open field in Pennsylvania as a result of an attempted cockpit invasion. However, there have been claims that it was actually shot down by US fighter jets. This idea is promoted by author David Ray Griffin in his book The New Pearl Harbor. Two debris fields from Flight 93 were found at three (Indian Lake) and eight (New Baltimore) miles from the crash site, and there are also some eyewitness reports of debris falling from the sky like confetti. However, Popular Mechanics argued that debris such as an engine exploding away and landing far from the crash scene is not a unique occurrence in commercial airline accidents. 
An Internet poster who uses the pseudonym "Paul Thompson" claims to have examined a number of mainstream media reports and says that fighter jets were actually much closer to Flight 93 at the time of the crash than stated in the official record. He mentions witnesses who noticed a small white jet near the impact site soon after the crash. However, government agencies such as the FBI assert this was a Dassault Falcon business jet asked to descend to an altitude of around 1500 ft to survey the impact. Ben Sliney, who was the FAA operation manager on September 11, 2001, says no military aircraft were near Flight 93.
Jim Hoffman notes a three-minute discrepancy in the cockpit voice recording immediately prior to the flight's crash. The cockpit voice recorder transcripts end at 10:03 a.m., but Cleveland Air Traffic Control reported that Flight 93 went out of radar contact at 10:06 a.m., and FAA radar records also note a time of 10:06 a.m. Seismologists record an impact at 10:06:05 a.m., +/- a couple of seconds. Despite this, the 9/11 Commission Report concluded that the crash occurred at 10:03 a.m.
Some internet videos, such as Loose Change, speculate that Flight 93 safely landed in Ohio, and a substituted plane was involved in the crash in Pennsylvania. Often cited is a preliminary news report that Flight 93 landed at a Cleveland airport; it was later learned that Delta Flight 1989 was the plane confused with Flight 93, and the report was retracted as inaccurate. Several websites within the 9/11 Truth Movement dispute this claim, citing the wreckage at the scene, eyewitness testimony, the difficulty of secretly substituting one plane for another and claim that such "hoax theories... appear calculated to alienate victims' survivors and the larger public from the 9/11 truth movement". The editor of the article has since created a rebuttal to the claims.
Jim Hoffman and the Scholars for 9/11 Truth and Justice are among those who have said the Flight Management Computer Systems on board Flights 11, 175 and 77 could have been loaded with a preset route that guided the planes to their targets. Boeing's technical specifications confirm that this is possible. Hoffman suggests that Flight 77 performed the unusual spiral dive it made on its approach to the Pentagon with the help of the onboard computer.
Some theories suggest that, rather than having preset routes entered into the planes' on-board computers, the planes were flown by remote control. The controllers of the planes may have been on the ground or, as in the "doomsday plane" theory, in another aircraft. This theory argues that a blurry white object seen in the sky in videos of the World Trade Center, was a plane containing the remote controller of Flights 11 and 175, and that an aircraft that flew away from The Pentagon after that impact contained the remote controller of Flight 77. The aircraft at the Pentagon was later identified as a E-4B National Airborne Operations Center (NAOC) plane, a militarised version of a Boeing 747-200, taking part in the Global Guardian exercise.
Remote control of Boeing aircraft is only possible with the installation of additional software and even then the pilots can override control by moving the yoke. Theories of remotely controlled aircraft have been criticised for ignoring phone calls made by passengers which state that their aircraft had been hijacked.
The BBC and the Daily Telegraph reported on September 23 that some of the people named as the hijackers by the FBI were actually "alive and well". One of them was Waleed al-Shehri, who they said they had found in Casablanca, Morocco. Abdulaziz Al Omari, Saeed Alghamdi, and Khalid al-Midhar, three other hijackers, were all said to be living in the Middle East. On September 19, the FDIC distributed a "special alert" which listed al-Mihdhar as alive (the Justice Department later said this was a typographical error). These reports have led to claims that the names of the hijackers may be incorrect, or that the hijacking scenarios outlined in the 9/11 Commission Report may not be the truth.
All of the reports have since been acknowledged as cases of mistaken identity by the publications involved and by other news organizations such as the New York Times. The BBC said that confusion may have arisen because the FBI names were common Arabic and Islamic names. In 2002, Saudi Arabia asserted that the names of the hijackers were correct.
Some attention has been given to news reports that might indicate that the named hijackers were not typical Islamic extremists. For example, Mohammad Atta reportedly ate pork, drank alcohol, gambled in casinos, and went to strip clubs.. It is however controversial whether terrorists are motivated primarily by religious belief.
Air phone calls and cell phone calls were placed from the hijacked planes. Conspiracy theorists say cell phone calls should either be impossible or rarely possible from commercial planes, and therefore the hijackings were staged and the phone calls were faked.
After 911, cellular experts said that they were surprised calls were able to be placed from the hijacked planes, and that they lasted as long as they did. They said that the only reason that the calls went through in the first place is that the aircraft were flying so close to the ground. Alexa Graf, an AT&T spokesperson said it was almost a fluke that the calls reached their destinations. Other industry experts said that it is possible to use cell phones with varying degrees of success during a flight.  Marvin Sirbu, professor of engineering and public policy at Carnegie Mellon University said on September 14, 2001 that "The fact of the matter is that cell phones can work in almost all phases of a commercial flight."
Based on a study he conducted in Canada in 2003 to determine whether and how well cell phones could be operated from aircraft, Canadian Mathematician A.K. Dewdney concluded that the chance of successful connections for the number of cell phone calls made from the planes used in the 9/11 attacks "can only be described as infinitesimal". Based on this, economist Michel Chossudovsky says that at least part of the 9/11 Commission Report chapter on the cell phone conversations, is fabricated. According to the 9/11 Commission Report, 13 passengers from Flight 93 made a total of over 30 calls to both family and emergency personnel (twenty two confirmed air phone calls, two confirmed cell phone and eight not specified in the report). The FBI Joint Terrorism Task Force testified that all but two calls from Flight 93 were made on air phones.  There were reportedly three phone calls from Flight 11, five from Flight 175, and three calls from Flight 77 which American Airlines later confirmed did not have airphones fitted; two calls from these flights were recorded, placed by flight attendants Madeleine Sweeney and Betty Ong on Flight 11. A conspiracy theory web site claims anomalies relating to the nature of the phone call transcripts.
Conspiracy theorists say they detect a pattern of behavior on the part of officials investigating the September 11 attack meant to suppress the emergence of evidence that might contradict the mainstream account. They associated news stories from several different sources with that pattern.
According to the 9/11 Commission Report, the cockpit voice recorders (CVR) or flight data recorders (FDR), or "black boxes", from Flights 11 and 175 were not recovered from the remains of the WTC attack; however, two men who worked extensively in the wreckage of the World Trade Center say they helped federal agents find three of the four "black boxes" from the jetliners:
"At one point I was assigned to take Federal Agents around the site to search for the black boxes from the planes. We were getting ready to go out. My ATV was parked at the top of the stairs at the Brooks Brothers entrance area. We loaded up about a million dollars worth of equipment and strapped it into the ATV. There were a total of four black boxes. We found three."
Ted Lopatkiewicz, spokesman for the National Transportation Safety Board, remarked that "It's extremely rare that we don't get the recorders back. I can't recall another domestic case in which we did not recover the recorders."
With the exception of the CVR from Flight 93, the black boxes from Flights 77 and 93 were either never recovered or were said to be too damaged to yield data. On April 18, 2002, the FBI allowed the families of victims from Flight 93 to listen to the voice recordings. In April 2006, a transcript of the CVR was released as part of the Zacarias Moussaoui trial. Some conspiracy theorists do not believe that the black boxes were damaged and that instead there has been a cover up of evidence.
A June 2007 video, attributed to researcher Calum Douglas of Pilots for 9/11 Truth, presents an analysis of alleged Flight 77 black box data, said to have been obtained from the National Transportation Safety Board (NTSB) under a Freedom of Information Act petition. It states that the approach path and altitude on the Flight Path Animation differs from the mainstream account of the path of Flight 77.
Bin Laden tapes
A series of interviews, audio and videotapes have been released since the 9/11 attacks that have been reported to be from Osama Bin Laden. At first the speaker denied responsibility for the attacks but over the years has taken increasing responsibility for them culminating in a November 2007 videotape in which the speaker claimed sole responsibility for the attacks and denied the Taliban and the Afghan government or people had any prior knowledge of the attacks. The Central Intelligence Agency has confirmed the speaker was or was likely to be Osama Bin Laden. Some people in the Muslim World doubted the authenticity of the tape. Steve and Paul Watson of Infowars.net claim that the organization handling the tapes is a front for the Pentagon and that the tapes are "highly suspect". Professor Bruce Lawrence head of Duke University’s Religious Studies Department and author of Messages to the World: The Statements of Osama bin Laden believes the tapes are fake and that Bin Laden has been dead since 2001.
- See also: Responsibility for the September 11, 2001 attacks#Other alleged responsibility
- See also: 9/11 advanced-knowledge debate#Foreign government foreknowledge
There are allegations that individuals within the Pakistani Inter-Services Intelligence may have played an important role in financing the attacks. There are also claims that other foreign intelligence agencies, such as the Israeli Mossad, had foreknowledge of the attacks, and that Saudi Arabia may have played a role in financing the attacks. Francesco Cossiga, former President of Italy from 1985 until his resignation over Operation Gladio, asserts that it is common knowledge among intelligence services the 9-11 attacks were a joint operation between elements in the U.S. Government and Mossad.
The theory that such foreign individuals outside of al Qaeda were involved is often part of larger "inside job" theories, although it has been claimed that, while al Qaeda deserve most of the responsibility, the alleged role played by Pakistan, Israel or Saudi Arabia was deliberately overlooked by the official investigation for political reasons.
"No plane" theories
Some individuals, primarily on the internet, have made the claim that no hijacked airliners hit the World Trade Center towers ('No Boeing Theories' or 'No Plane Theories'). Supporters of this claim have been described as "no-planers," or "Pod people," by members of the 9/11 truth movement who generally maintain that the claim is a case of poisoning the well — an effort which is intended to broadly discredit the more credible theories. According to "no-planers," live television, video and photographs that purport to show Boeing airliners on September 11th all had fake airplane images composited into them. Many prominent members of the 9/11 Truth Movement have rejected the claims.
Those describing the no plane claims as poisoning the well often refer to proponents like Morgan Reynolds, former Labor Department chief economist under George W. Bush, who calls himself the "black sheep" of the 9/11 Truth Movement. Reynolds claims he believes that the Boeing planes of Flights 11 and 175 could not have impacted the Towers and has proposed that digital compositing was used to depict the plane crashes in both news reports and subsequent amateur video. Numerous papers by 9/11 Truth Movement researchers have rejected the claims.