I do not think that is a particularly interesting category in this context, even though it might present somewhat difficult challenges with regard to collision

I do not think that is a particularly interesting category in this context, even though it might present somewhat difficult challenges with regard to collision avoidance and scheduling (if we ever get to that point, "drone pollution" will probably become an issue.) I think it is fair to say that, in the context of the article we are all responding to, the relevant sector of commercial aviation is that which currently uses airplanes flown by human pilots.