The 2nd World Trade Center Attack - flittering object

Flittering object is probably a helicopter or plane that was acting as a spotter plane for the attack on the World Trade Center. The helicopter or plane was probably unmanned and could capture images which it would continuously stream, and this information could be sent to operators, who would then operate controls from the "missile plane". Hence the operators could observe what was happening from "inside" the plane, as the plane probably had SATLINKS and they could also observe the plane from externally and close by through flying a helicopter drone nearby the tower.