[terminalshort]

Can emit all bytes except for 00000101 isn't really the type of problem you see in a digital system. And even if it were, it's pretty simple.

plane 1 > assign code 4563

plane 2 > reject

plane 1 > assign code 0827

plane 2 > accept

Also assigning short codes like that isn't something likely to be necessary in an automated protocol like this. Why not just have every message sent between 2 planes include a sender_id: UUID header?

[rogerrogerr]

Because now we’re talking about putting deeply integrated equipment in every plane. It’s a certification and cost nightmare.

This is not a system where you get to do clean slate greenfield development. Whatever you do must work for the lowest common denominator. ATC is a fairly cheap societal expense compared to developing, certifying, installing, and maintaining systems with the level of integration you want in hundreds of thousands of diverse planes.

[terminalshort]

There are only 35,000 commercial planes on Earth. Even if installing costs $1 million per plane, that's only $35 billion.

[rogerrogerr]

The US has about 200,000 general aviation planes. You can’t ignore them, and you can’t just ban GA because that’s your pipeline for getting commercial pilots.