Get thee to a counsellor, do not let those fears overtake your life. There are some good programs out there that may help allay your fear of flying, fear of travel, fear of anything. PTSD is manageable, it starts with admitting there is a problem and actively seeking out assistance for yourself, not because of or for him, but for you.
Those of us who were/are supporters do not want anyone to do the thinking for us. If we support/love you, it is because we see the souls within, because you are human and a good person, and have all sorts of good qualities that make us want to be around you, like any normal relationship. Who doesn't have issues and baggage?
As Purplemunchkin said, communication is the key, but don't make him your therapist. Find someone you like, whom you can work with, and who wants to work with you. It is a big, beautiful world out there, and I understand the fears. When you realize you have them, it is time to do something about them. No one expects you to go skydiving or anything, but maybe in time you will be able to travel a little with the right help.
And it doesn't hurt to take him to a session or two with you, if agreed upon with a therapist. They can help keep your thoughts and explanations calm and rational.
Good luck - don't write him off because of your own perceptions of yourself and how you are going to bring him down. Talk to him, find help and things can be better with time and hard work. What we supporters like to see is someone who is willing to try, as difficult as it may be at times.
