Your Jepp charts (if your company uses them) should have a map of the frequency coverage for AIRINC. The East coast is serviced by New York radio, the rest of the US is serviced by San Francisco radio. It is a subscription service, plus connect fee and per minute fee.
If you are out of normal radio range (Acars and voice) for dispatch, ops, etc this service is usually available above 5,000.
Airlines also use it for MedLink, a patch to a doctor for medical emergencies.