I would just like to add that simulating FAC(A) is a great advanced task for multiplayer play.
The purpose of a FAC doesn’t revolve around the technological challenges of simply designating a target for someone else.
The key is the word “close” in close air support. The FAC ensures the integration of and the safety of friendly joint forces that are in close proximity to the enemy targets – both ground and air assets.
There are all kinds of chaotic and dangerous activities going on short of the FSCL. You want to minimize fratricide and make sure the targets you hit are in keeping with the ground force commander’s current needs. Control measures and the FAC are used ensure proper integration.
In short, the FAC makes sure both air and ground assets are dancing to the same sheet of music.
Also, the 9-line is just the start of communication between the FAC and CAS packages that arrive on station. Essentially they are the details that explain the current situation and begin the process of the FAC controlling each attack. It’s the FAC’s job to maneuver and clear the fires of the CAS a/c – given a menu of three specific types of control and methods of attack.
I’ll not go into more detail, but I encourage you to learn more and then try it out.
p.s. all the posts here about simply passing off targets to other aircraft, etc. That’s called terminal guidance operations (TGO). Not exactly the same thing as a FAC–lacks the FAC’s authorities and control.