* The date of the attack itself is the first clue. 9/11, add the digits together (9 + 1 + 1) and you also have 11
* September 11th is the 254th day of the year: 2 + 5 + 4 = 11
* After September 11th there are 111 days left to the end of the year
* The Twin Towers – standing side by side, looks like the number 11
* The first plane to hit the towers was Flight 11.
* Flight 11: 92 onboard, 9 + 2 = 11
* New York City: 11 letters
* The Pentagon: 11 letters
* George W Bush: 11 letters
* Colin Powell: 11 letters
* Afghanistan: 11 letters
* Ramzi Yousef: 11 letters
* Flight 175: 65 on board, 6 + 5 = 11
* Flight 77: 11 x 7