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Chronology of 9/11 terrorists events

Timeline offering intelligence details of connections between 9/11 attacks and other worldwide terror bombings.
/ Source: NBC News producer

August 22, 1998 - Nairobi Embassy bomber Mohamed Rashid Daoud al-Ow'hali admits to FBI agent in Nairobi that he has received instructions re: the bombing from an al Qaeda operative in Yemen, named Ahmed al-Hada. Al-Hada, say U.S. officials, manned a "terrorists' switchboard" in Yemen, a cell phone used to relay messages between Al Qaeda leadership and its operatives. Al-Hada's daughter is married to man named Khalid al-Midhar, a Saudi who on September 11 flies an American Airlines plane into the Pentagon. It is unknown when the CIA and FBI realize the relationship between al-Hada and al-Midhar... if they ever do before September 11.

April 7, 1999 - Khalid al-Midhar gets multiple entry visa from U.S. consulate in Jeddah Saudi Arabia. The visa is good for a year and can be renewed.

December 1999 - Telephone intercepts of conversations among known al Qaeda operatives are overheard by U.S. intelligence in Yemen, indicating an important meeting is about to take place in Kuala Lumpur, Malaysia. The calls were apparently overheard on the "terrorist switchboard" operated by al-Hada. In any case, the calls generate notifications to CIA stations worldwide to be on the lookout for those believed to be traveling and Malaysia authorities are asked to check out locations identified in the intercepts.

January 3, 2000 - An attempt to blow up the USS The Sullivans in Aden harbor fails when a Zodiac boat loaded with explosives sinks in the harbor. U.S. is unaware of the attempt until much later, following the October 12, 2000 bombing of the USS Cole.

January 5, 2000 - Al-Midhar begins his journey to Kuala Lumpur, apparently with Nawaf al-Hamzi, another terrorist who joins him on September 11, 2001 in piloting the American Airlines jet into the Pentagon. As he is transiting a friendly, unnamed country, his passport is examined and information about it is passed on to the CIA in near real-time. The CIA notes the existence of a multiple entry U.S. visa and reportedly informs the FBI...even before al-Midhar arrives in Kuala Lumpur in the early evening. In an email read to NBC News, the FBI confirms receipt of information, but FBI claims there was "some confusion" about al-Midhar's name.

January 6, 2000 - At a meeting hosted by Malaysian militant Yazid Sufaat are among others, al-Midhar, al-Hazmi, and another Yemeni named Tawiq bin Attash, also known as Khallad, who U.S. officials knew was an al Qaeda fighter and who they would later link to both the attempted bombing of the USS The Sullivans and the successful bombing of the USS Cole. The purpose of the meeting is still not known, but the U.S. ultimately learns the condominium was later used by at least one other September 11 participant, Zacarias Moussaoui indicating it was some sort of a safehouse. Malaysian authorities photograph participants, but do not video tape them or bug the meeting

January 7, 2000 - Al-Midhar and Al-Hamzi leave Kuala Lumpur on a flight to Los Angeles...unbeknownst to Malaysian intelligence and the CIA

January 8, 2000 - Other participants in the meeting leave for other locations.

January 15, 2000 - Al-Midhar and Al-Hamzi arrive in Los Angeles after a stopover in Bangkok, Thailand.

March 2000 - A friendly intelligence agency informs the CIA that al-Hamzi has flown into the United States. CIA does not inform the FBI or other agencies. Al-Hamzi is later determined to have been living in San Diego with a listed telephone number.

April 2000 - Al Midhar and Al-Hamzi enroll in the National Air College in San Diego.

May 2000 - Al-Midhar and Al-Hamzi have their first flight lesson at another San Diego flight school.

Mid to late 2000 - Al-Midhar leaves the United States and stays overseas, mostly in Southeast Asia and Middle East, not returning for nearly a year.

September 2000 - Al-Hamzi opens a bank account at the Bank of America branch with a $3,000 deposit. He also purchases a 1988 Toyota Corolla for the same amount, obtains credit cards and Social Security numbers under their real names.

October 12, 2000 - Al Qaeda bombs the USS Cole in Aden harbor, killing 17.

October 2000 - U.S. investigation in the Cole bombing links Tawiq Khallad, who participated in the Kuala Lumpur meeting nine months earlier, to the USS Cole bombing and the attempted bombing of the USS The Sullivans, raising the importance of the links between him and al-Midhar and al-Hamzi. CIA tells no one.

October 2000 - Zacarias Moussaoui, the so-called 20th hijacker, visits the same condominium in Kuala Lumpur visited by Al-Midhar and Al-Hamzi. No indication his trip was monitored in real time by U.S. or Malaysian officials. Moussaoui is given $35,000 and a letter of introduction from a company called Infocus, leaving shortly thereafter for the United States.

January 2001 - Al Hamzi, having flunked out of flight school in California, joins another September 11 hijacker Hani Hanjour at a Phoenix flight school.

January 2001 - CIA finds picture of Khallad with al-Midhar in the Kuala Lumpur file, further establishing the link between the Cole bombing and Al-Midhar. CIA tells no one.

February 23, 2001 - Moussaoui enters the United States, arriving In Chicago on a flight from London, having already flown from Pakistan to London.

March 19, 2000 - Al-Hamzi buys flight training videos from Ohio Pilot Store.

February 26, 2000 - Moussaoui begins flight training in Oklahoma, spending nearly two months in Norman, OK.

April 1, 2001 - Al-Hamzi leaves California and heads east. On his way, he is stopped for a traffic violation in Oklahoma. Oklahoma State Trooper C. L. Parkins ran Alhazmi's California driver's license through the computer, checked to see if the car was stolen and made sure there wasn't a warrant out for Alhazmi's arrest. When nothing came up, he issued the terrorist two tickets, totaling $138, and sent him on his way. If the CIA or FBI had put him on a watch list, it could have shown up during this check. U.S. officials believe that Al-Hamzi may have been meeting with Moussaoui at this time in Oklahoma.

April 2001 - CIA was alerted to Zacarias Moussaoui by an informant who knew the Frenchman only by an alias and the agency didn't link the two names until well after Sept. 11, government officials say. The informant mentioned a man by a different name that he had met in 1997 during a gathering of Islamic extremists.

May 2001 - Moussaoui makes first contact with Minnesota flight school while still in Norman.

June 10, 2001 - Al-Midhar renews his multiple-entry visa into the U.S. while in Saudi Arabia.

July 4, 2001 - Al-Midhar reenters the United States for the last time.

August 13, 2001 - Moussaoui begins flight training in Minnesota.

August 13, 2001 - Al-Hazmi, Mohammed Atta, Marwan al-Shehhi, and two "muscle men" from Atta's plane meet at the Econo-Lodge in Las Vegas.

August 17 2001 - Moussaoui is arrested in Minnesota on immigration issues after flight school instructors grow suspicious of his desire to fly commercial jets and inform the FBI.

August 23, 2001? - FBI asks French intelligence service for information on Moussaoui, a French citizen.

August 23, 2001 - CIA, after a "scrub" that also produced the intelligence provided the President a week earlier, informs the INS that Al Midhar and Al-Hamzi should be stopped if they attempt to enter the United States. INS informs the CIA that it is too late, that they have entered the US. CIA informs FBI who begins frantic search for the two men.

August 25, 2001 - Al-Midhar buys plane tickets for American Airlines Flight 77.

August 27, 2001 - French intelligence service responds to FBI, linking Moussaoui to Islamic militant groups.

Robert Windrem is an NBC investigative producer, based in New York.