Agree with stut's advice. I used to have panic attacks all the time - usually related to being in a confined space (as opposed to any kind of fear of flying). I've taken lots of yoga and now just try to practice good breathing techniques to avoid hyperventilating.

I'm much more likely to have a panic attack walking through the airport or in the boarding area than I am sitting on the plane - I don't like the sensation of being "trapped" in a moving crowd.