That's quite an understatement.
Actually, the kingdom's involvement was deliberately covered up at the highest levels of our government. And the coverup goes beyond locking up 28 pages of the Saudi report in a vault in the US Capitol basement. Investigations were throttled. Co-conspirators were let off the hook.
Case agents I've interviewed at the Joint Terrorism Task Forces in Washington and San Diego, the forward operating base for some of the Saudi hijackers, as well as detectives at the Fairfax County (Va.) Police Department who also investigated several 9/11 leads, say virtually every road led back to the Saudi Embassy in Washington, as well as the Saudi Consulate in Los Angeles.
Yet time and time again, they were called off from pursuing leads. A common excuse was "diplomatic immunity."