I got a mailing from the manufacter of Byetta the other day (since Im a user) and it was all about airline travel and Byetta. Byetta has been put on the "approved meds" list that you can bring on a plane, so they won't give you a hard time about your penlet or its needles if you do one thing. Bring a letter from your doctor and put that right on top of your meds as they go through the scanner belt. The other thing I find really helpfull is to put your pen in the original box it comes in BECAUSE they always paste your prescription lablel on the box. This shows that it is a prescription med and WHAT type of med it is. The box and the plastic holder for the penlet also serve as insulation if you put the thing in a little mini cooler with ice packs.
Yes, you have to take one of those things that holds like a six pack, put "ice packs" in it, and then your meds. REMEMBER to wrap your Byetta in a plastic baggy or the original box as you don't want to get it wet as the icepacks melt and sweat. YOU CANNOT, I REPEAT-CANNOT use the factory Byetta travel case with the Gel pacs. Even the manufactuer of Byetta warns against trying to take this onboard as they just aren't gonna allow the gel packs! Besides, if you are flying to Europe or farther, you are really better off with icepacks and a small insulated carrier as this will keep your Byetta cold for 8-16 hours.
I have a little more faith in the airlines than you do and I put mine in my checked luggage on a recent trip and it fared just fine, but if you want to carry it on board, you have to do the above. Hope this helps all you lizard spit and pen users.