FFS - are people really this stupid?
Why would someone blow up a building when they know a plane is going to crash into it (or nearby) anyway ?
Do you understand how silly your scenario is ?
"Sh*t, we've just discovered that WTC7 was actually blown up. We must keep this a secret as the American people will cope with commercial, domestic planes filled with passengers being crashed into an iconic building in their largest city but simply will not put up with a smallish building being blown up. WE MUST NOT LET THIS GET OUT !!!!"
Do you have any concept of risk versus reward ?
Here we have a scenario where the 'evil geniuses' basically have zero reward (unless you are one of those that think Americans would not have been sufficiently outraged without WTC7 being blown up

) and a whole lot to lose.
It seems every month this thread gets dumber and dumber.