This discussion has been around for a long time. Since I was your age, I would estimate.
I have seen the discussion take shape many times. It started with discussions of whether or not the aircraft had been modified. Then came assertions that humans could not survive the maneuvers made by the aircraft that hit the pentagon (which was cute).
It even got to the point where people were claiming the GDI Ion Cannon took the thing down (I shit you, not:
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That one has been floating around since at least 2006 in some form or another.
There are a rare few people who present the rational questions and want answers to the gaps in our knowledge of what happened and the conflicting reports that had been given over the disaster.
The thing is, to believe something like 9/11 was a 'false flag' operation is to believe that people are fundamentally evil. Even if we were to assume that the hijackers were CIA operatives and it was just aircraft that hit the towers (no other grand conspiracies); it still is the belief that well over a hundred people that would have to be involved, directly, in such an operation are so fundamentally evil that they would commit to killing thousands of their own countrymen.
If you doubt the idea that a jet liner could bring down those buildings - then you are looking at expanding that conspiracy to thousands of people - all of whom have to be willing to see loved ones die for 'hush up' money (or that there is an even greater conspiracy in a group of people so corrupt as to intimidate vast numbers of people into complying with a conspiracy where their own country, possibly their own family, was attacked).
The more I have learned about how things work in the intelligence and operations side of things, the more I believe we are looking at a rogue element. The CIA had been working with many different groups throughout the middle east as their efforts to overthrow Russian authority were well underway. It's quite possible that the people who committed the attack on U.S. soil were part of an older program to train militants in the fight against the Russians.
Following the fall of the USSR - Congress took an ax to the CIA and quite literally decapitated it. Thousands of informants were left flapping in the wind and entire branches of our human intelligence networks literally withered. The staff who knew about these operations were all cut loose, and the entire CIA lost touch with many of its former programs (and were more than likely funding more than a few operations they had no idea what they were).
Without any oversight - this group then would have received instructions to carry out an attack. Or perhaps they dreamed it up, themselves. The point is that the CIA no longer had positive control over something they brought in years ago under different administrations.
Then the attack happened.
At that point, everyone would have gone into CYA mode. Agencies would realize their connections to these individuals and that something had gone horribly awry. Documents would be shredded, stories would be rehearsed, and a target would be found for the unfolding aggression.
The number of people who know the full story is likely very small, if it exists at all. What I present is merely speculation.
Even if it could be confirmed that this is what happened - it could almost never be proven that the attack did or did not originate with Bin Laden. It is quite likely that the agencies at the time could not have known this one way or the other (but it is a possibility that shifts the heat onto something other than the CIA, FBI, CNN, NBC, ABC, 123, ETC).
Or it could be exactly as we are told. There are a lot of gaps in our understanding, and a lot of questions that will likely never be fully answered. Those questions will likely die with our generation as future generations are taught about events they did not live through and did not experience.
