I think many of the hurdles involve how intricately humans are involved in the air traffic grid at all levels.
AI is a product but moving planes around is wildly complicated. Getting pilots to obey you can be a crap shoot.
These guys will get in arguments. The pilot not wanting to deviate or slow down and the controller trying to arrange his grid. If one pilot doesn't obey it can create danger.
They've talked about upgrading it for decades. The cost and the transition and retraining involved is incredible.
Make no mistake, there have been upgrades but they are expensive and small.
One such upgrade happened early 2000ish. The big visible change was the ATC could change the background color of the radar from black to dark blue.
No.
The united states air traffic control grid is so old and so archaic the cost of upgrading would be 100's of billions.
It is so old they still use vacuum tubes.
My AI avatar would be wildly inaccurate.