You may want to check out:

www.tribiketransport.com

You basically drop off your bike at a local participating triathlon store and they deliver your bike right to their expo area at the race. When you finish the race, you return your bike to the area and then they bring your bike back to that triathlon store where you dropped it off. You don't need to disassemble your bike or worry about it getting dinged up by the airlines. I haven't used their service, but I've heard good things about it. It got a good write-up in one of the recent triathlon magazines.

Definitely don't pack your bike in a cardboard bike box. I did that one time and TSA put a hole in my disc and refused to pay for it. You can get good boxes for around $250 if you don't want to use the bike transport service.

+1 I used them for CDA and it was flawless. The only downsides are 1) they pick up your bike days (a week?) in advance of the race so you can't ride unless you have a spare; and 2) there is usually a line after the race to drop off/return the bikes to be shipped back to you.

The remedy to the long line is as follows: When you do your packet pick-up, they give you a bike voucher that says, "Hey, whomever holds this ticket can pick up the bike for ndtriathlete." It is like the Golden Ticket from Willy Wonka. Give this ticket to your girlfriend/boyfriend/wife/mistress whomever, and have THEM pick up your bike after T2 and take it directly to the TBT tent. They get to wait in a much shorter line while you are out on the run. (Just tell them not to touch the seat. And don't tell them why. Giggle and let them figure it out.) Then when you finish and you want to collapse, you don't have to wait in a long line like I did at CDA, waiting for TBT to take your bike.

FYI - I do have a $400 plastic clamshell and yes, I have used it for one race. I shipped via UPS to IM Wisconsin and insideoutsports.com had a deal to receive, assemble, disassemble after the race and ship home for a fee. They may still, so look into it. I was very happy. But I am using the box again for IM Germany (via American Airlines). And $100 round trip isn't bad. I've been quoted $80 each way. So, two uses in four years. Not such a good ROI.

Another option is to contact your local bike shop and/or bike group. Someone has a box to rent, loan. I've loaned mine out to others so at least it gets used. The only condition is that they must put a sticker from their race on it.

Whichever you choose, the cardboard box trick is a no-no.

TriBikeTransport here, too! I used them for IMKY last year, and it was awesome. They are a great company. And being able to just walk the bike 30 yards from transition back to them after was also great.

I used TriBike Transport for IM California 70.3 a couple of weeks ago. I live in NJ so I had to drop it off almost two weeks before the race. With that in mind, I wouldn't do it any other way. I flew Continental and they have a $100 bike fee each way. Some people manage to not pay it, but I wasn't going to take any chances. I think it cost me about $225 and I shipped a gear bag with it for an additional $25. Very convenient location and I didn't have to do anything with the bike except take off the pedals.

Another vote for TriBike Transport. That is such a convenient service. I'm using it for the second time for IMCdA....and were driving to the race! I just feel better having them take the bike and me not having to worry about it. Particularly after the race when we take a few days' vacation in Montana.

That said I did recently fly with my bike in a Trico Sports Iron Case, that I borrowed from someone. Had to do some disassembly of the bike to get it in the box (so aero base bar could fold down flat) and wrapped my 404s in bubble wrap to be sure that as they overlapped they wouldn't get smashed or scuffed. And yes, I was very nervous about the whole thing. When I arrived at my destination I checked in the box and found everything to be in order. I did end up spending a good portion of my first day at my destination building the bike back up (I packed some tools in the box too so that I could rebuild on my own). I paid $80 each way on United. Overall it went well for me. But still if TBT is an option for your race do that.