It's not - it's much simpler. Drivers move in a 2D plane densely populated with cars and things that are not cars. Planes sparsely populate the sky by themselves. (There are birds too, but not that high up, and they're largely unavoidable in real-time anyway)
There's already semi-automated collision avoidance. If two planes are on a collision course, TCAS tells one plane to climb and another to descend. This works because outside of tightly managed scenarios like a holding stack, and planes shouldn't be anywhere near each other horizontally. There are no other planes above or below you (or anywhere nearby) and by fixing the directions as up and down, TCAS doesn't even have to calculate compass bearings that would work for avoidance.
There's already semi-automated collision avoidance. If two planes are on a collision course, TCAS tells one plane to climb and another to descend. This works because outside of tightly managed scenarios like a holding stack, and planes shouldn't be anywhere near each other horizontally. There are no other planes above or below you (or anywhere nearby) and by fixing the directions as up and down, TCAS doesn't even have to calculate compass bearings that would work for avoidance.