Have to admit, my company (MYT) is vert strickt as to when to wear it, you don't wear it in the terminal as one of my colleagues said before, but you don't go out on the ramp or anywhere near the a/c without one! also with your ID on show and you ear defenders... dont really see many other airline crews wearing them downroute, but its silly not to, if its provided... wear it! when you get hit by ground service trucks who you gonna complain to when the airilne provided ya hi viz and you didnt wear it?