I've flown using almost every imaginable bike case at one time or another. This is what I've been using lately: http://bitingduck.com/?q=node/19

YMMV, offer not valid with any other discounts, and if your bike arrives flat as a pancake don't blame me, though I haven't had any trouble with it and find it more convenient than a hard case. Most recently I added a frame (made from 2x4's and a fork mount from performance) that works the same way as the internal steel frame in a bikepro case. I've also been using closed cell foam sheets that they sell for putting on your garage floor instead of the cardboard shown in the pictures.