I didn't take the time to look up all 19, but the ringleaders (Mohamed Atta, et. al.) entered on nonimmigrant visas. https://en.wikipedia.org/wiki/Hijackers_in

I didn't take the time to look up all 19, but the ringleaders (Mohamed Atta, et. al.) entered on nonimmigrant visas. https://en.wikipedia.org/wiki/Hijackers_in_the_September_11_attacks https://en.wikipedia.org/wiki/Hijackers_in_the_September_11_...