China Southern.
Jesus wept. If, in trouble, anyone knew precisely when to turn the radio on, nobody would ever get lost! They were conserving..... Conserving, both battery and personal energy. Why would they have the radio on at midnight, 30k nth of Marree? The system worked. Even if they did hear China Southern, would either party have understood the other? Doesn't matter, two fine people came home to their families. The system worked!