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I second the ground effect tardis, and have done since I got back from travelling with it for a year...
my bike was a genesis flyer, but with pipe lagging cable tied on it got me round the world, and the bike was still in one piece...
Also if you haven't loaded the bag with clothes and other such stuff, it's easy and light enough with bike to carry using the shoulder strap.buy one here.
http://www.groundeffect.co.nz/products/tardis-compact-bike-bag
Ground Effect Tardis might be worth a look - I've used it for multiple flight/train trips and no damage so far. Packs down pretty small when not in use.