[ASA Vet]

According to the site you linked, none of the 9/11 terrorists were here on an immigrant visa.
They had either non-immigrant tourist or non-immigrant student visas.

[grey_whiskers]

They had either non-immigrant tourist or non-immigrant student visas.

Agreed completely.

But they still had overstayed, with nothing done about it!

And these were, as you point out, tourist, or non-immigrant visas, which are SUPPOSED to be merely transitory...

...so overstaying should have been a real red flag.

Cheers!