Airlines still think kayaks are 12' long. Or they don't realize there is a difference between sea kayaks and playboats.
Buy the canvas travel sack for your kayak and say it is a surf board or a surf ski: Salamander Rodeo Yak Wrap
The bag totally hides the boat, makes it look like a surf board or just another piece of oversize luggage, and has convenient handles. When the airline see it, they say no problem, just an easy piece of oversize luggage. The bag costs $100, the airlines will charge you $75 each way. I did this on United last year.
If only going to Phoenix, you may want to ship it. Forward Air should be about $50-75 each way. You'll need the bag above. The easy way to ship it is to just go to Confluence kayaks. Confluence will wrap it for $25, but buy the bag--it makes it easy.