Key events in the growing number of conspiracy theories surrounding the 9/11 attacks.
Operation Northwoods: A proposal is drafted by military planners, exploring options for generating support for US action against Cuba.
These ideas included simulated terrorist actions by the American government. Another suggestion was the shooting down of an unmanned drone masquerading as a civilian airliner.
The plans were sent to the US defense secretary for approval, but were never implemented.
More than 40 years on, the two concepts - that of false-flag terrorist operations against civilians, and of using a drone aircraft to simulate a civilian plane - have led to conspiracy theories claiming that the US government was capable of using the same tactics on 9/11.
The first two 9/11 hijackers arrive in the United States via Los Angeles international airport.
Nawaf al-Hazmi and Khalid al-Mihdhar were already suspected of involvement in al-Qaeda terrorist activities by the CIA, which had been monitoring their movement abroad.
But the CIA does not inform the FBI, so the two terrorists do not appear on the terrorist Watchlist - and as they have valid visas are allowed in the country.
Al-Hazmi and al-Mihdhar settle in San Diego where they live openly, using their real names in official documents. One is listed in the local phone book.
They start lessons at a local flying school, but are soon rejected because of their poor English.
In August 2001, the CIA finally warns the FBI that al-Hazmi and al-Mihdhar may be in the United States, but by then the two terrorists have long gone from San Diego and cannot be traced.
9/11 sceptics have expressed doubts about the official account of how the two Al Qaeda operatives were able to live undetected for so long.
An American think tank, the Project for the New American Century, publishes a report called Rebuilding America's Defenses: Strategy, Forces and Resources For a New Century.
The report advocates the transformation of the US military, making it better able to support their aspiration for an active, internationalist US foreign policy.
But, the authors acknowledge: "the process of transformation, even if it brings revolutionary change, is likely to be a long one, absent some catastrophic and catalyzing event - like a
new Pearl Harbour".
This line has attracted the attention of critics, who argue that 9/11 may have been an attempt to produce the "Pearl Harbour" effect.
However, PNAC report does not advocate a catastrophic act, it merely predicts the possible consequences of one.
Among the reports signatories, Paul Wolfowitz who later became number two at the Pentagon, and Lewis "Scooter" Libby, who went on to become chief of staff to Vice President Cheney.
11 SEPTEMBER, 2001
According to the official account, four commercial aircraft were hijacked. Three were deliberately flown into buildings, and the fourth crashed in a field in Pennsylvania. 2,996 people were killed.
0846: American Airlines Flight 11 crashes into the North Tower of the World Trade Centre.
The World Trade Centre's south tower collapses after the attacks
0903: The second plane, United Airlines Flight 175, crashes into the South Tower at the World Trade Centre.
0937: In Washington DC, American Airlines flight 77 crashes into the Pentagon. Conspiracy theories suggest the crash is suspicious because there is no publicly available CCTV footage clearly showing an aircraft hitting the building and because the damage caused to the façade appears too small to have been caused by a large commercial jetliner.
0945 approx: Delta Airlines flight 89 is diverted to Cleveland airport because of initial suspicions that it may have been hijacked. The local mayor gives a press conference in which he says:, "The initial reports was that this plane was hijacked and that there was a bomb on it". It is quickly established that Delta flight 89 has not been hijacked and corrections are broadcast by the local media, but the first inaccurate reports continue to be the focus of conspiracy theories.
1002: United Airlines flight 93 crashes in open ground near Shanksville, Pennsylvania. Conspiracy theories argue that the plane never crashed here, because there are no large pieces of visible wreckage at the scene. It is also alleged that the plane was shot down, and broke up in mid-air, spreading debris over a wide area.
1720: World Trade Centre Building 7, a 47 storey building close to the two main towers collapses. It was not hit by either of the two hijacked aircraft. 9/11 conspiracy theories suggest that it was destroyed deliberately, because it held sensitive or compromising documents in the offices of the CIA, Department of Defense and Secret Service, which were housed in the building.
12 SEPTEMBER, 2001
Immediately after 9/11 a conspiracy theory developed that Israelis and or Jewish citizens had been warned to stay away from the area by someone with foreknowledge of the attacks.
The story, which was untrue, originated in Beirut, quickly spread across the Middle East and was picked up by anti-Semitic websites around the world.
10 NOVEMBER, 2001
President Bush confronted the growing proliferation of 9/11 conspiracy theories. Speaking to the United Nations in New York, he said: "We must speak the truth about terror. Let us never tolerate outrageous conspiracy theories concerning the attacks of September the 11th; malicious lies that attempt to shift the blame away from the terrorists, themselves, away from the guilty".
French journalist Thierry Meyssan publishes 9/11: The Big Lie and Pentagate - his accounts of 9/11 which suggests that American Airlines Flight 77 did not crash into the Pentagon.
The Federal Emergencies Management Agency (FEMA) releases its report into the causes of the collapse of buildings in New York on 9/11. Chapter Five describes the collapse of World Trade Centre Building 7, which FEMA suggests was caused by prolonged fires weakening the strength of the trusses which supported the building.
Publication of report by the joint Congressional inquiry into intelligence failings leading up to the 9/11 attacks.
Over 30 pages in the published version have been redacted by the government, because of national security concerns.
It later emerges that most of the redacted pages relate to the activities of the first two hijackers in San Diego and to their possible connections with Saudi Arabian nationals living there.
The inquiry's co-chairman, Senator Bob Graham, feels that the FBI, in particular, withheld evidence about the activities of the two hijackers who lived in San Diego.
22 JULY, 2004
The publication of the 9/11 Commission Report provides the public with the most comprehensive account of what happened on that day, but its findings fail to stem the flow of conspiracy theories.
The American Magazine, Popular Mechanics publishes a major investigation called Debunking the 9/11 myths. The article is later extended into a book.
Loose Change, a film produced by first-time director Dylan Avery is released. The film is distributed primarily via the internet and rapidly becomes a worldwide phenomenon, watched tens of millions of times.
Loose Change takes issue with many aspects of the official account of 9/11, including the collapse of the Twin Towers and WTC 7, the crash of American Airlines 77 into the Pentagon and United Airlines flight 93 at Shanksville, Pennsylvania.
It is the most popular of a growing number of internet films challenging the official account of events on 9/11.
Other examples of the genre include The 9/11 Mysteries and Alex Jones' Terrorstorm.
James Fetzer, a retired professor of philosophy founds the organisation Scholars for 9/11 Truth - a movement dedicated to "exposing falsehoods and revealing truths" about 9/11.
16 MAY, 2006
CCTV footage of the Pentagon is released to Judicial Watch, a Washington based foundation advocating accountability and transparency in government.
The footage, from two security cameras, shows a blurred object approaching the building immediately followed by a massive explosion. But the quality of the video is poor and the evidence is inconclusive.
Judicial Watch subsequently obtains the release of further security camera footage from the FBI. But these images, from a nearby petrol station and hotel, are not sufficiently detailed to satisfy sceptics.
Evidence from the case of Zacarias Moussaoui is published on the internet.
In 2005, Moussaoui pleaded guilty to conspiring with the 19 al-Qaeda hijackers. Much of the evidence relates to the events of that day, including photographs of the crash sites and documents belonging to the hijackers.
25 October, 2006
The State Department publishes a website on The Top September 11th Conspiracy Theories, as part of its Identifying Misinformation website.
12 SEPTEMBER, 2006
Pentagon Inspector General declassifies a report assessing the performance of the US military on 9/11.
The Inspector found that members of the military had misinformed the 9/11 Commission about events on the morning of the attacks, but that this had been down to poor record keeping and bureaucratic muddle.
There was no evidence, wrote the inspectors, that the military had sought to deliberately mislead the members of the 9/11 Commission about the events that day.
FEMA is expected to publish the final report of its investigation of the collapse of World Trade Centre Building 7.