One good thing to know about flying a bike is that smaller airlines, (such as Soutwest, Alaskan, or Allegiant) will charge far less or a bike than major airlines (Delta, Continental, United). If you can book your ticket so that you check your bags initially with a small airline, you will pay their baggage fees, even if you are connecting to a major airline later in the trip.
With smaller frame sizes, you can sometimes break the bike down into two boxes. You generally get 62 linear inches for packing, and you may be able to fit the frame in one box, with the fork, bars, stem, seatpost, and wheels in another box. For padding, just pack your panniers and clothes around the bike parts. This route can be pretty tricky, and does require some extra mechanical know-how, but it can be another option.
My last suggestion, which can be risky, is to purchase a bike near your arrival destination, and try to line up a buyer for the used bike when you are finished with your trip. Just make sure you can get racks on the bike, or perhaps a trailer.
Thanks, and good luck.