parishiltons, in my Centre that is impossible as when they check in on frequency they may not be either logged on yet or at the correct flight level whereby CPDLC is permissable, and there are too many instantaneous instructions to every aircraft to permit soul use of CPDLC. For departures I will only use voice until they are about transfer point and then CPDLC may come into effect, but it is near on impossible to just use CPDLC for an entire transit of any flight through any of my sectors.