I'm obviously late to this discussion which seems primarily focused on the technical aspects of making GS happen in this or that bird. My question is how is this going to be made to work in the real world? Programming a flight plan and turning a craft loose to do it's own thing assumes that there's nothing else in the air - perhaps possible in very remote areas, but in populated areas, i.e., those with all manner of air traffic? Did I miss something in my understanding of what GS is?
I'm not raising the issue of what may or not be legal now or in the future, rather the common sense issue of avoiding mid-air collisions. What have I missed here?