While we're talking about 121.5...
ATCO in small tower in SW England. We have a scanner receiver in the tower so we can keep an unofficial ear on traffic in adjacent airspace on quieter days. One of the scan channels set is 121.5 which I was taught (not that long ago) was the International Distress Frequency. All I seem to hear on it is (and forgive me if this is unrepresentative!) US military flights and French/Spanish sched flights calling each other 'On Guard' and often as not, in French or Spanish.
What is 'On Guard' and why is the distress frequency used like this? Must drive the D&D people mad!
Cheers,
DinD.