It's kind of funny to reflect that we fly along designated air routes (railway tracks in the sky) at set altitudes within +/- 50 feet vertically and +/- 100 metres laterally to such an extent that two a/c pass each other head-on at 1800 km/h in the middle of absolutely nowhere on a regular basis with only 1000' of separation. The much reduced probability of this happening if aircraft used random tracks and altitudes in remote areas (no ATC) would seem to be a far better option sometimes.
Someone with a brilliant theoretical, but practical mind will solve this problem sometime in the future and we will all sit back and say, why didn't I think of that?