On both 9/11 and 7/7 (911 days after 9/11) the governments were running drills identical to the actual attacks that occured on the same day. This is done for a reason, so government employees whose purpose is to listen to "chatter" simply think that it's all part of the exercise while the rogue participants can carry out their plan without interference. Also, if anyone is caught, they can simply say they were participating in the exercise.