So if/when the now infamous Bin Ladin Determined To Strike in US memo landed on his desk on August 6th, 2001 - or the even earlier “UBL [Usama Bin Laden] Threats Are Real" memos from months earlier; they would have been taken seriously and acted upon.
Acted to do what? Implement TSA in January of 2001? Create DHS inside the first 100 days? Put air marshals on planes by June?
Intelligence knew about the pending attacks, but had no real way to interface with airport security. That was the root of the problem. And nobody was going to solve it until after 9/11 because Congress would not have taken this any more seriously than they took it during Blowjob Gate, when Al Qaeda was taking pot shots at the USS Cole.