It's also further evidence that our continuing to uphold them as a model ally is absurd in the face of how we purport to feel about human rights.
Edit: even this document puts the word "ally" in quotes when speaking about Saudi Arabia.
Edit 2: upon further reading, not only may they have had knowledge of it, but they may have provided material support to the hijackers after they arrived in the US. Is there further information about this anywhere credible?
Edit 3: most information about the actions of these people after September 11 is still redacted.
Edit final: this release is pretty damning, although I'm not an expert in this field. There is maybe an angle here? Is the US government about to distance itself from SA? Or is something more damning about to become public? Tin-foil theories to be sure, but I feel like things like this rarely get released without a FOIA fight.
2 of the hijackers could possibly be Saudi intelligence officers
The US has a limited understanding of Saudi government involvement and their role is unknown.