According to a declassified CIA intelligence report on June 1, 2003: “We believe that a common thread runs between the first attack on the World Trade Center in February 1993 and the attacks on 11 September 2001. [Redacted] named KSM [Khalid Shaykh Muhammad] as either the mastermind or one of the key planners of the 11 September operation. KSM, the uncle of Ramzi Yousef, who masterminded the 1993 bombing plot against the World Trade Center, provided financial and logistic support for the 1993 operation.”
– CIA, “11 September: The Plot and the Plotters,” (CTC 2003-40044HC, CIA Intelligence Report), The Central Intelligence Agency’s 9/11 File:, The National Security Archive, June 1, 2003