More to the point, there's no need because we're already very close to hitting the theoretical maximum flight distance - the point at which you could connect any airport to any other airport - which is slightly less than 13,000 miles [0]. Call it about 12,300.

The A-350ULR has a range of a bit more than 11,000 miles [1].

Basically, probably some time in the next decade or so we will break through that barrier and be able to connect any two airports on Earth nonstop if we wanted to. Whether it is economical to do so is another question.

[0] http://www.gcmap.com/mapui?DU=mi&P=AGP-AKL

[1] https://www.flightglobal.com/a350-900ulr-range-figure-not-a-...

While I fully agree with the first paragraph, I question the second.

The risk to humans in automated flight is mainly in takeoff and landing. I can readily imagine making safe UAV tanker drones which take off and land on airstrips far from human habitation, such that the occasional mistake, while expensive, costs no human life.

What I can't imagine is the economics of this ever working out.

The safety issue would also apply for mid-air refueling; that’s a precision maneuver that would endanger the crew of the cargo plane. Plus, if the cargo itself is expendable you’d be just as safe handling the cargo planes the same way as you suggest handling the fuel drones.