All in all, the CIA knew the Sep 11 attack before it took place.
As a matter of fact, the CIA admitted they had an intel related to the attack beforehand, but they claimed that they had not grasped the detail, which was said to be the reason why they failed to intercept the terrorist act.
However, their claim was a well-calculated lie. I paid a visit to the targeted sites in the previous two weekends guided by the spy as the intelligence community including the CIA had understood the exact target and probable timing in advance. I assume I was not the only one framed by them to be related to the Sep 11 attackers.
The CIA apparently noticed those attacks beforehand, but it does not mean all the CIA employees grasped them ahead of time. If we just claim that the CIA recognized the Sep 11 attack when all the officers knew it in advance, they can always claim that they did not know, as all the information have never been shared within the agency.
Their intelligence network captured the exact intel about the Sep 11 attack, which was delivered to the ranking officers in the chain of command. That basically meant the CIA knew the terrorist act in advance, but they left the terrorist to attack the sites.
I mentioned some figures until here; a Korean who was availed to frame me as a terrorist, a Japanese police intelligence chief who was one of the mastermind who set me up as a terrorist suspect again in the US, a CIA officer who definitely knew the Sep 11 attack in advance.
I have a confidence that I can prove enough that they knew the Sep 11 attack beforehand, though the intelligence community is likely to support these insiders at whatever cost, as they knew and conducted more unforgivable operations which the community worried to be revealed to the public eyes.
Having said that, I assume it has been already investigated which ranking officers knew the terrorist attack in advance. As you can imagine, the US Department of Defense would not accept to let it go as they were one of the main targets of the Sep 11 attack.
The majority of the fundamental issues have been uncovered until now, but I had no idea whether it was made public or not. On the other hand, there is a large possibility that all the information will be revealed to the public in the intelligence file against me when I am dead.