Someone hijacking a plane to crash it was not too damn bright to start with.
Their goal was killing people, hijacking a plane they thought would be shot down would accomplish that, just not get as many killed as crashing it into buildings. Either way they cause mass death.
There were a lot of people working and making decisions that day, and a lot of confusion (even in the news). That is not to say there was no conspiracy, that the US government had nothing to do with it, etc. Never accept carte blanche the government line on things, but in the same vein I can see this as being a cluster f*ck as people were uncertain with so many planes in the skies what all was going on and who to shoot down if anyone.
I will accept the base premise as presented for now, but will continue to look deeper for clues. If we accept that premise as presented there is still enough to warrant a change in power as so many did not perform the jobs they were hired to do. On top of that we have to examine the root causes as to why they would want to attack us, which still goes back to * and crew somewhere along the line. It does not give them a right to kill people who had nothing to do with the perceived ills they were addressing in their actions - two wrongs don't make a right.
In the end we must get more answers - if you or I do something the government will investigate the hell out of it and demand answers to everything they ask under oath, they need to do the same until we have all the answers we seek. If they reserve the right to imprison people and interrogate them for information, they damn well need to come before us and answer a lot more questions.
I will keep an open mind, I won't just accept any theory that comes along, but I will examine it. I don't see a vast conspiracy where hundreds of people all knew and covered it up, and given how many see * as an idiot I see the 'caveman' theory as being more likely than him carrying it out

Just some random thoughts, I have more and may delve into them later when not so tired.