With Update 20.1, new airspace boundaries are coming to Infinite Flight, as well as the addition of Center. Tower’s airspace strictly extend to the innermost boundary of the airspace rings, but controllers may still on guard from 25NM out and below 10,000ft if there is no Approach. Departure and Approach’s airspace extends to FL180 vertically and 50NM laterally.
Center’s airspace extends to FL600 vertically and within the white boundaries and outside the innermost airport ring laterally if approach is not active. If approach is active, Center’s airspace extends to FL180 within Approach’s lateral boundaries and to the surface everywhere else.
For more information, see section 5.1 of the Infinite Flight ATC Manual.