September 11 - Khalid Sheikh Mohammed

According to the findings of the 9/11 Commission, the plot to simultaneously hijack four American planes - and then crash them into significant U.S. buildings - was devised by Khalid Sheikh Mohammed.

This image of the alleged mastermind is from the 9/11 Commission Report, chapter 5, image 1.

Credits

Photo, from the 9/11 Commission Report - chapter 5. 

U.S. National Archives.