[Kurn, son of Mogh]

The 19 hijackers didn't have to be let in on visas

This is a misunderstanding of the issue. The problem is that the US never checked Visas or passports in detail on exit. Nor did we have a system to flag individuals who overstayed their Visa time limits. Those kind of checks might well have prevented 9/11.

I don't think there was anything "questionable" enough about the backgrounds of these 19 that would have triggered anything that would have kept them out. At least not under the funding and staffing levels of the intelligence community for the 5 years preceding the event.

People always want to point fingers and say "here's where the blame goes." That may be human nature, but its wrong. In a free society there is always risk.