ATC...

Requests...
To listen the ATC you must request first. See the Requests section for the available requests. If the ATC still not talk, have a look to the FAQ...

ATC Type...
The ATC you talk with can belong to one of the following kind of control areas. The ATC type is edited in the flight planner through a dropdown list.
As in real life, the clearances or information the ATC will give depend on the kind of ATC it is: you cannot have a taxi clearance from a CENTER or DEPARTURE controller!
The ATC Type is also used to build the callsign of the ATC in the messages. ATC callsign (for example Dallas) and ATC Type (Departure) are concatenated to build the whole callsign (Dallas Departure).

APPROACH or DEPARTURE
At this stage there is no much difference in terms of ATC behaviour between Approach and Departure. Select the one you want for the spoken callsign. When talking to that type of ATC...

• VFR flight becomes VFR special 
• Landing information (not clearance) can be delivered
• APPROACH can ask for holding patterns (only IFR)
• Can deliver flight clearance (see Taxi chart section)

CENTER or FIS

• VFR remains VFR
• Are just supposed to answer (always approving!) to transit in, report, altitude change requests
• One day, they will give some traffic information

GROUND

• Deliver taxi clearance

INFO

• Same behaviour than CENTER and FIS
• Not that this Type is used as a "tag" when editing the runways in a Taxi chart

TMA

• VFR become VFR special randomly (See Constants section to modify the probability of being turned into VFR special )
• Similar to APPROACH and DEPARTURE behaviours

TOWER

• VFR flight becomes VFR special if you requested to land or if you are within a STAR or a SID
• Can deliver pretty much everything

ATC behavior...
Many things can be improved in the way the ATC gives you clearances. That the most interesting part of the plugin to program! So feel free to give me feedbacks...
WIP...