Only those in the cockpit needed to know. The rest were in charge of subduing the passengers and could have been told they were hijacking the plane for ransom, or to meet demands, or any other story. If you consider the long lead up to 9/11, keeping most operatives in the dark makes the most sense for an Al Qaeda planners since it reduces the chances of a member talking or dropping out.
"FBI investigators have officially concluded that 11 of the 19 terrorists who hijacked the aircraft on 11 September did not know they were on a suicide mission"
Interesting. Good link. Yet, that still means that 8 of them knew. Not like it was 1 out of 19.
There have also been plenty of other suicide bombers at much smaller targets. Generally I don't think they are that excited about blowing themselves up, more they are willing to do it to take care of their families financially when they don't see any other options.
Could you share a link to that? What part of "fly plane into building" didn't they understand?