I just now read regional traffic control centers, which link all the others, got overloaded with data traffic because the FAA communication system is a patchwork mess - multiple generations of new tech integrated with old legacy systems and each other over a long span of time. That kind of setup can be nursed and prodded along for years by dedicated maintainers, but at some point the upside-down Slurpee cup that's been holding up one end of the shelf crumples and everything falls on the floor.