Not sure what you are referring to when you said drone? It always look like to me it was from previously placed explosives inside like to do for other building demos, are you saying it may have been something else?

The CNN footage from the day has about 2 seconds of a greenish air vehicle approaching the towers before the second strike. it has a bulb in the front, and wings significantly different than a 757 or 767 - but just about the same as a US military heavy drone. However, the drone, even with explosives, wouldn't make a wing-shaped hole in steel collumns. So, coordinated (mostly) explosives.