Air traffic is an entirely different matter to autonomous UAS (aka drones). The current problem with Air Traffic Management systems is that they are based on a 1930's air traffic control concept procedural control. All attempts to update the concept are mired by 'experts' in the 1930's concept who can only think in its terms. So trajectory based operations where an aircraft's future 4D positions are known allow the aircraft to fly in a way that is considered efficient by the operator (what Europe is calling the 'business trajectory). This is simple for automation to deal with and reduces airspace congestion and has been demonstrated in large scale research. However, the implementing ANSPs do not understand the concept and try to force 'trajectory based control' into their 1930's procedural concept and it becomes 'time based control' (the 4th dimension) and unsurprisingly the problems seen in today's system remain. There's more but it's not for this thread nor this log
