Of course it was planned, Tahloube. There is no way that a military operation of that size could be mounted in that short a time. As I wrote previously, there are always plans and they are updated frequently in areas of strategic interest. Since Al Qaeda had been operating freely out of Afghanistan for a number of years, and Al Qaeda had claimed responsibility for attacks on US interests abroad and domestically, there is no question that plans were under continual update and intelligence gathering was intensive since the mid-1990's.
I believe where you make a grievous error in understanding is with the word, "planned" in which you imply activity for which there was no evidence -- an arranged pretext for triggering the events. I believe this maybe due to a fundamental misperception of the ability of the USA to keep a secret. It cannot keep a secret. It never has been able to. The news media since this country's inception has published every bleeding activity, legal or illegal, real or imagined, ascribable to the national government. Our government works in a most peculiar way -- it takes advantage of human weakness to protect the people from the government. Each branch is deliberately set at odds with the other two branches. There is a constant probing for weakness to exploit. And it is all laid out for the public to inspect.
Even the most secret information can, with a subpoena, be brought to court or Congress for review.
The possibility that anybody in the US gov could have planned or covered-up some theoretical "real" cause of 9/11 is beyond ludicrous. Conspiracies simply cannot survive in a competitive environment. The truth will out.
Conspiracy theorists are left with "negative" evidence to support their theories. This is the evidence like, "they should have seen", "they should have known" etc.
When looking at the night sky or daylight clouds, the human mind cannot help but impose patterns on the celestial sphere. Our brains are hard-wired for pattern recognition. We simply cannot help it. Even when there is no pattern, we see one.
In closing, I suggest you read the 9/11 Commission Report. It was assembled by a group of highly competitive, very partisan members who are wise to the ways of government and knowledgeable of the intelligence community. The footnotes are especially interesting because tehy provide an extremely unusual glimpse into the hidden world of the intel community.
For your conspiracy to float, it would have to either include these guys as part of a vast conspiracy or they had to be dupes. I can hardly imagine a less likely scenario. It puts the burden squarely on the conspiracy theorists and requires the theorist to produce more than negative evidence and cloud patterns.