everything with a mass over 1kg+- in the air, is carrying a "gps" and something that is transmitting its location, and all air traffic world wide is(theoreticaly) assigned a flight path for each trip,witha specific flight level, ie: the planning is 3d, so the density per layer, never gets very high, and there are specific paths taken to change layers, there are never any dogs, or horses, or people trying to deek, there are no signs or maps, and in case of fully automated vtol
taxis, navigation will be to mm accuracy, with likely a routine to land fully autonomously on loosing the network, and a backup ballistic recovery parachute, if power is completly lost or another emergency situation occurs.
and also likely is that forward speeds will be low enough, that collisions with birds will be a low probability, and rotors will likely be schrouded, keeping the idiots heads attached when determinidly trying for that gota have selfie.