Very year, tens (if not hundreds) of thousands of bikes get shipped from China to the U.S. in the very same boxes that you get from your LBS via boat then truck with possibly rail thrown in. Just pack in like it is when shipped from the factory. Or pay a LBS to do it.

Also, have you considered the UPS/FedEx option for domestic travel? It can often be cheaper than flying. We went that route for out last two tours out west. Last year, we shipped two bikes (one in a cardboard box and one in a semi-hard case) and a third, smaller box containing a B.O.B., my racks, stove and empty fuel bottle. Total shipping cost from Philly to Missoula was around $200 one way. That was much less than what the airline wanted for the two bikes alone ($350). We used the savings to pay to have the bikes assembled and tuned and waiting for us upon arrival. The shop also held our boxes and re-packed and shipped the stuff home at the end of the trip.

Heading out to Cycle Oregon on Friday. We will be lying with the bikes this time because we are flying Southwest. The bike charge is only $50/each.