Originally Posted by Coldhands

Can I just stick it in a thick clear plastic bag (protecting the sensitive areas with cardboard etc) and check it in or will airlines say 'that's a bicycle' and try to charge you something?

Yes, you can pack your bike this way. But I wouldn't recommend it. Depending on airline; bicycle surcharge(applies to folding & non-folding) and risk of damage. Even if the baggage handlers are careful - there's always a chance it might fall or get stuck on the conveyor belt.

In your experience are airline/bus/train etc staff any bit hostile to folders? I'd love to hear your experience!

I don't like confrontations & arguments. This is why I always have my bike in a cardboard box or suitcase. Folding bikes must be covered at all times on Japanese trains: