[pure speculation] Hmmm... 9/11 (NYC), 3/11 (Spain), 6/11??? [/pure speculation]
Interesting speculation. Who knows? You might be right. These folks sure love their "symbolism."
6/11??? YOU MAY BE ONTO SOMETHING.
To continue your speculation:
5/11
"A masked man had read out a statement before the killing which was signed off with the name of Zarqawi and dated May 11."
http://www.freerepublic.com/focus/f-news/1133477/posts