So keeping a listening watch on 121.5 is a requirement and plays a part in PLOC?
I've thumbed through a few docs but can't find the Standard. Is it in ICAO, EASA, CAA or another regulatory publication?
https://www.eurocontrol.int/sites/de...ction-plan.pdf
http://www.icao.int/APAC/Meetings/20...%20-%20rev.pdf
http://www.skybrary.aero/index.php/Guarding_121.5_MHz