That's fancy (and less intimidating) talk for Aedolis' main military training complex. While common military personnel might receive training at any of several facilities, all Pilot candidates report to the ATC for their training regardless of which city they hail from. A massive, warren-like complex, the ATC contains both classrooms for instruction and larger rooms that are used for drills and simulations. It is so large that necessary facilities exits in multiples, there being a number of cafeterias, infirmaries, barracks, and others within the ATC. In the center of the complex are a small group of lead rooms, used to isolate and punish candidates who have been severally insubordinate or under suspicion.
There is a midlevel entrance that is accessible by approved civilians on certain days of the year, where they can spend time with the candidates in a special lobby.
Like all of Haviah, access within the ATC is set up vertically. The higher stage a candidate is, the higher up in the ATC they will live and operate.