the existing systems deliver the international standards for air traffic management that needs to move in sync for all parties, ATC, Airports, Airlines, Manufacturers and Regulators. Technology suppliers to each of those parties where they differ will need to be involved in anything material.

there are many systems involved to manage different parts of flight, are built to spec and integrated deeply across all the parties

even if the systems are old in some cases, they deliver the agreed standards, so updates need to be agreed via organisations like ICAO or IATA and rolled out via a predictable timeline through a managed change process

this is all integrated with human processes, such as for the flight deck