February 26, 1993: An attempt to blow up the WTC fails. Six people are killed in the misfired blast. Analysts later determine that had the terrorists not made a minor error in the placement of the bomb, both towers could have fallen and up to 50,000 people could have been killed. The attempt is organized by Ramzi Yousef, who has close ties to bin Laden. [Congressional Hearings, 2/24/98] The New York Times later reports on Emad Salem, an undercover agent who ends up being the key government witness in the trial against the bomber. Salem testifies that the FBI knew about the attack beforehand and told him they would thwart it by substituting a harmless powder for the explosives. However, this plan was called off by an FBI supervisor, and the bombing was not stopped. [New York Times, 10/28/93] Why did the FBI seemingly let the terrorists go ahead with the bombing? Several of the bombers were trained by the CIA to fight in the Afghan war - the CIA later concludes in internal documents that it was "partly culpable" for this bombing attempt. [Independent, 11/1/98] An Israeli newsweekly later reports that Ahmad Ajaj, an associate of Yousef, may have been an mole for the Israeli Mossad. At the time of the attack he is serving a six-month sentence for having entered the country on a forged passport, but he was involved in the planning of the bombing. The Village Voice has suggested that Ajaj may have had "advance knowledge of the World Trade Center bombing, which he shared with Mossad, and that Mossad, for whatever reason, kept the secret to itself. [Village Voice, 8/3/ 93] US officials later state that the overall mastermind of the 9/11 attacks, Khalid Shaikh Mohammed, is a close relative of Ramzi Yousef, [Independent, 6/6/02] probably his uncle. [Los Angeles Times, 9/1/02] One of the attackers even left a message found by investigators stating, "Next time, it will be very precise." 9/11 can be seen as a completion of this failed attack. [AP, 9/30/01]

Early 1995: In the wake of the uncovering of the Operation Bojinka plot, a letter written by the terrorists who planned the failed 1993 WTC bombing (see February 26, 1993) is found on a computer disk in the Philippines. This letter warns that future attacks would be more precise and they would continue to target the WTC if their demands were not met. This letter was never sent, but its contents are revealed in 1998 congressional testimony. [Congressional Hearings, 2/24/98] The Manila, Philippines police chief also reports discovering a statement from bin Laden around this time that although they failed to blow up the WTC in 1993, "on the second attempt they would be successful." [AFP, 9/13/01] Why wasn't security at the WTC noticeably improved after these revelations, or later?