Mode S should solve frequency change problems when available all over Europe.
Waiting for that, we've got in the ops room a list of companies we can reach via ACARS. But I think those companies must have ops in france (not sure) so a message can be send with the right frequency.
It doesn't solve the problem for pilots who listen to 121.5 when it's crowded. It shoudn't be !
Usually, pilots say "12345" when they want to chat. I've never heard "1215".
What is this "practice Pan" procedure ? Do people use the emergency frequency for training, or ...???
