Hi,
I normally buy one kind of these:
http://www.amazon.de/Velosport-Faltg.../dp/B001V8HQPM
The bike fits under it. The big advantage is that the wheels are open and the service personal can roll the bike. Alternatively in some airports it's possible to wrap the whole bike in a plastic foil - this is a quite good possibility to pack it. This even prevents scratches.
Thomas