Earlier quoted context omitted.
Is there an actual reason why the control tower work can't be fully automated? For train control lights we almost don't rely on human operators anywhere.
Trains run on fixed tracks with fixed intersections, and one track might see a handful of them per day. Planes around airports come in from all directions in three dimensions, and there can be hundreds of arrivals per hour. These are vastly different scales of problem domain.
In the middle of nowhere. A metro track can have a train every 60s.
But it's still entirely fixed, with easy to deploy sensors on both the tracks and trains.