In reply to PeterM:
> It's a polystyrene type, not unlike a cycle helmet. I'd imagine it'd be easy to snap or crush. Maybe a hardshell ABS helmet would fare better. If it hadn't been mentioned to me I'd have probably just put it in hold luggage without much thought.
It's the lack of thought that is probably the issue
If you pack well with your helmet in the centre of our bag with a rolled up towel or fleece inside it aand either your rope or more clothes around it you should be fine. I've got away with at least twice a year for the last10 to 12 years.
Bear in mind that you will always hear more from one person who packed badly than the many who have got it right.