Padded Wheel bags.
You can pick up some plastic hub protectors from the LBS, they probably have a pile of them that they'll give you.
Do you have a carbon stem or carbon handle bars? If not it really isn't a big deal to take the handlebars off and zip tie them to the frame. 10min job.
It's best to choose the smallest case that you can and do some disassembly (seat post, handlebars, derailleur, and pedals) so you can pack as tight as possible so nothing rattles around. The baggage handlers will abuse your luggage in ways you can barely imagine.