This is dumb. I would bet there's nobody in the world except a couple of rappers and a few dozen terrorists would even have considered the possiblity that people would coordinate an attack by hijacking 4 (5? 6? 7?) planes at the same time and flying them into prominent buildings. That's just nuts and nobody can predict nutty behavior
After the massacre of the Israeli athletes by terrorists at the 72/ Munich Games a investigation looked into how such attacks could be prevented in the future. One finding was that the terrorists could use hi jacked airliners to fly into buildings , stadiums etc.