How'd they know? In advance?
Same for WTC7. How'd they know? Impossible to have predicted it. WTC7 looked completely intact one second, the next a pile of rubble barely taller than a man.
Do such things happen in real life? Of course not. They do however happen in dramatic theatre and narrative fiction. Somebody was telling a story that day and reality seems to have altered itself to suit their tale. Such things do not happen in the real world in such a precise and timely fashion.
Who was on board those planes? The government admits it has no idea. None at all.