Are you sure you want to go with that?
The report detailed evidence of contacts between al-Qaeda and Iran, noting that at least eight of the hijackers passed through Iran between 2000 and 2001 without having their passports stamped.
While this sounds like Iran helping the hijackers, it's nothing more than normal Iranian law, which doesn't stamp visas into passports.
It was well-known, for example, that if a Saudi traveled to Afghanistan via Pakistan, then on his return to Saudi Arabia his passport,
bearing a Pakistani stamp, would be confiscated. So operatives either
erased the Pakistani visas from their passports or traveled through Iran, which did not stamp visas directly into passports.