I haven't flown domestic with a bike since 911 (that's what mini vans and station wagons are for!).

I have used both a hard case and a bike-box in the past. Both went on the airline just fine; but that was before all of the new "we must search every piece of luggage" madness started. Would I want some stranger unpacking and re-packing my bike? No.

What the others said about airline fees is true too. Expect $50-80 each way.

So if you can part with your steed a few days in advance, shipping is a pretty good option. Personally? I wouldn't pay for the extra fee (weight, plus buying/renting)for a hard case. Guess how your bike got from the factory/builder to the bike shop in the first place? Yep, one of those thick corrugated cardboard boxes. Ask your shop to save some of the plastic spacers for the fork, and some foam tube-padding, as well. Remove the stem and tape the stem/bars to the frame. You'll also need to remove your pedals/front wheel. I always pack extra (lightweight) cycling clothes and accessories around the bike as "padding". You can fill in the rest with bubble-wrap and/or wadded up paper.

Shop around for shippers too. Some good bike shops will ship shop-to-shop for you (some even include dismantling/packing/reassembling the bike). If you go the DIY route, you might find that you save by going directly to UPS or FedEX. Some of those "pak-n-mail" places add extra fees.

Have a great trip!
We are going to TN (Gatlinburg) at the end of March and I am looking forward to some good climbs!