I once took a friend flying who was scared of heights, in a PA28. His fear was that he would open the door and jump out - it's on the passenger side, of course, in the PA28. No amount of persuading him that if he didn't do it, it wouldn't happen, or indeed that you can't open the door against the airflow anyway, would make him happy. We got from Kidlington to Enstone before we had to turn round, and he emptied the hip-flask of whisky he brought with him on the return trip. Luckily I was driving...
He won't come again, so I haven't been able to work on a cure.
Tim