I have 6 transport planes right now, and four divisions of 3 brigades each, I tried doing two orders of two divisions, and then one of one. My air superiority is either null, because neither of us have any airplanes (C. China v Afghanistan) or, if I tell the transport planes to be active in that region, 100%. But I don't know if telling them to do is neccessary, or prohibitive to actually making the drop.