Hey Chris - If you haven't used the rod yet and, if possible, I would
highly recommend that you trade in for a 4 piece!
The issues with flying with a two piece rod are numerous. Four piece rods are simply so much easier to deal with and they can go in your luggage. No need to check another item - which it seems everyone is charging $$$ for now-a-days! I'm dealing with the same thing for a trip to Santa Fe we're about to take!
I was trying not to have to check a bag, but no matter what I do it looks like I'm going to have to - and that's another $25 one way!

Unless, you get to fly Southwest apparently...
We've got no choice on this trip...Otherwise - I'm not real sure there's any great options. They may even charge something extra for a long item like that today! It's getting to where I'd rather drive - quite annoying!
A gun case comes to mind, but then you'll be on the suspicious person list! I sat on a plane in a gate in LA one time because, as the pilot stated - honest to God -
"There's a suspicious bag in the hold!"That's a great thing to tell a plane load of people, isn't it?

But probably the best move would be some heavy gauge PVC and even that isn't all that safe. An employee of one of the Shreveport airlines came into my shop years ago with four or five broken rods
(that they broke), wanting to know if they could be fixed.
I asked her if the guy had them in a case and she said he did, but they closed the bay door on it!
Go back and get the four piece, and put it in your suitcase!