http://www.infowars.com/its-time-to-admit-the-911-truthers-were-right/
The 28 pages confirm that the saudi funders were continually investigated in the USA and every time the FBI got close, higher ups shut down the investigations.
Combine that with the fact the saudis were protected upon the event of 9/11 and sheltered out of the country then invited back for tea, cigars and celebration leaves no doubt.
At a minimum the govt was complicit in the coverup. At the worst, they were telling the saudis who to pay and how to arrange it.