Originally Posted by
TomMM
7/5 UA53 ZRH-IAD Ch9 available^ although I didn't hear anything during the Oceanic portion of the flight.
Over the ocean, most communications are handled by
CPDLC. The radio that is usually connected to "Channel 9" is set to frequency 123.45, an air-to-air frequency that's usually just chatter between aircraft. If voice communication is required, an
HF radio is used (vs the VHF radio used over land).