alt Hacker NewsAirplane radios are generally broadcasting and receiving mono. There are modern headsets that can also play stereo, but only for onboard music or intercom purposes, if the plane supports it. But in planes with 2 radios you can usually configure their I/O individually. So you can listen (and also talk, although that makes sense less often) on two frequencies at the same time.
Yes of course, the transmitted audio would be mono. I meant one radio in one ear and another radio in the other ear, or if you mix them and they both play in both ears. But it sounds like they're mixed (talking over each other in a single audio stream).