If any one person was responsible to prevent the 9/11attacks, it was the National Security Advisor, Condi Rice. She told the 9/11 Commission and the 9/11 Widows that the "Bin Laden Determined to Strike in US" memo did not warn of upcoming attacks. The memo warned of preparations for hijackings and planned attacks inside the USA with explosives. The widows came to call her "Kindaliesalot Rice".
The widows gave the 9/11 Commission 300 questions. They only got 27 answers. They gave Condi 65 questions and got 7 answers.
On July 10, 2001, CIA director George Tenet and Richard Blee warned Condi that al Qaeda attacks were coming in the next few weeks. Later they said that if she had acted on those warnings, 9/11 might have been prevented. Cofer Black said "The only thing we didn't do was pull the trigger to the gun we were holding to her head."
There were also warnings from 13 foreign countries, and 3 FBI offices. The UK, Germany, Italy, and Egypt specifically warned of aircraft as weapons. Russia warned of suicide pilots. Jordan and the Cayman Islands warned of attacks involving airlines. France, the UAE, Taliban, India, Morocco, and Argentina also warned. Israel warned of 19 terrorists inside the USA planning something big, and even named at least 4 of the alleged hijackers.
The video also provides support for the report in the German press that the August 6 PDB was actually 11-1/2 pages long, not the 1-1/2 pages we have been shown.
Here is the transcript of Dr. Rice's statement to the 9/11 Commission and her answers to questions:
Here is the text of the "Bin Laden Determined to Strike in US" memo
Transcript: Bin Laden determined to strike in US - CNN