Chris Isham Events (3) August 22, 2001: Top FBI Al-Qaeda Expert Leaves FBI in Frustration; Misses Important Warnings 2001-08-22 August 23, 2001: Former FBI Al-Qaeda Expert Begins Job as Head of Security at the WTC 2001-08-23 March-April 2001: Al-Qaeda Defector Describes Plot to Hijack US Airplane