Apparently Karen Black is nearly Deaf and Mute
Joe Patroni is told that the air traffic controllers can barely hear "Nancy" the stew on the radio, and she can barely hear them. Joe tries out the radio, and it's true; Communications are faint and static filled, even with the benefit of a headset
However just a moment later, Joe's wife bursts into the cockpit, grabs a loose microphone at the flight engineer's station, and has a perfectly clear conversation with Joe while listening on a cockpit speaker with a hole in the plane.
So was Karen Black just a deaf mumbler or what? Lol.