It seems that airline operational staff on the ground have the ability to initiate verbal communication with airline pilots on at least some airliners, in flight.
Obviously pilots can communicate with ATC using, for example, VHF radio.
Perhaps, even in aircraft where phone service is not available to passengers, pilots in the air and/or airline staff on the ground can
- initiate a voice call using telephony equipment that is separate from any PSTN (public switched telephone network)?
- using existing headset?
- using aircraft internal intercom handsets?
- some means of selecting the call recipient?
- send text messages over the data links (e.g. via ACARS (Aircraft Communications Addressing and Reporting System) through VHF (very high frequency) or SATCOM (satellite communication))?
- use private VHF frequencies to communicate with airline operations?
If any of this is true, how does this work from the perspective of a pilot, steward or an airline operational staff member on the ground?