Shawn, I do have several suggestions that may help you. First you should seek a pain management specialist who can help you control your pain. Second would be to invest in a moist heating pad to take with you on the trip. Also ask your doctor about getting a muscle relaxer. That has always helped me tremendously.
Find out if the aircraft has enought leg room, so that you are able to stretch your legs out. Keep a few soft pillows with you to ellivate your legs. I hope these suggestions will help you. Good-luck! Dee