Hypothetically speaking....
To be text book perfect might take some work, but then some idiots went to school to learn how to fly..... didn’t they???
Lots of effort and advance planning went into 9/11. All pre meditated.
I’m sure that if a person wants to do do it, even if he’s just a “janitor” , with keys and night access/ 24 hour access, it would not be that difficult.
Particularly, if America is sleeping and no experience with islam and terror.
You just have no idea.