They use third party telecom providers to relay communications between ATC “centers” and remote radio transmitters. It is not purely AM radio and outages have occurred in the past, most recently in September.

https://www.nbcdfw.com/news/tech/a-calamity-disrupting-hundr...

Sure, but these are no longer connected to the controller's microphone via a long cord anymore.

That is true but nowadays the control rooms are separate from the actual antennas / areas being served. These are wired up with more modern comms.