Have packed rods on planes using PVC many times and have never had a problem. I wrap the rods in bath towels and duck tape the towels so they don't slip. Once you get the rods packed, duck tape a strap of some sort to the PVC tube. Find the right place to tape it and it makes a great handle. You will be glad you have a handle when you're carrying your tube through the airport.

Also, MAKE SURE you know what the airline allows when it comes to fishing rods. You can find this information on the airline's website. I always print a copy of their 'rules' and keep it handy in my carry on bag... I flew Continental to Mexico last year and I couldn't pack a rod over 6'6".