Secret documents reveal that the three Qatari men conducted surveillance on the targets, provided “support” to the plotters and had tickets for a flight to Washington on the eve of the atrocities.
The suspected terrorists flew from London to New York on a British Airways flight three weeks before the attacks.
They allegedly carried out surveillance at the World Trade Centre, the White House and in Virginia, the US state where the Pentagon and CIA headquarters are located.
Ten days later they flew to Los Angeles, where they stationed themselves in a hotel near the airport which the FBI has now established was paid for by a “convicted terrorist”, who also paid for their airline tickets.
Hotel staff have told investigators they saw pilot uniforms in their room along with computer print outs detailing pilot names, flight numbers and times and packages addressed to Syria, Afghanistan, Jerusalem and Jordan.
On September 10 they were booked on an American Airlines flight from Los Angeles to Washington, but failed to board. The following day the same Boeing 757 aircraft was hijacked by five terrorists and crashed into the Pentagon.
But, instead of boarding the American flight, the Qatari suspects – named as Meshal Alhajri, Fahad Abdulla and Ali Alfehaid – flew back to London on a British Airways flight before returning to Qatar. Their current location is unknown.
Investigators are also hunting a fourth man, Mohamed Al Mansoori, who they say supported the alleged terrorist cell while they were in the US.
The man, who is from the United Arab Emirates, previously lived in Long Beach, Los Angeles. His current location is also unknown, and US officials recommended that he is put on an international terror watch list because he “may pose a threat to aviation in the US and abroad”.
The details of the secret 9/11 team have emerged in a secret American government document obtained by the Wikileaks website and passed to The Daily Telegraph. It was sent between the American Embassy in Doha and the Department for Homeland Security in Washington.
The document, sent on 11th February 2010, states: “Mr Al Mansoori is currently under investigation by the FBI for his possible involvement in the 11 September 2001 attacks. He is suspected of aiding people who entered the US before the attacks to conduct surveillance of possible targets and providing other support to the hijackers.”
Details of the unknown 9/11 alleged plotters has never previously been disclosed. An official inquiry into the 9/11 attacks, which killed nearly 3,000 people, indicated that the hijackers may have received assistance in Los Angeles but investigators did not publicly provide more details.
The 9/11 Commission report, published in July 2004, states that at least two of the hijackers previously visited Los Angeles but, at the time, investigators appeared to have little information on their movements. The report states they had a "brief stay in Los Angeles about which we know little".
Only one person – Zacarias Moussaoui – has been tried and convicted over involvement in the 9/11 attacks as all the terrorists died in the crashed planes. Moussaoui, accused of being the twentieth hijacker, was sentenced to life in prison.