I don't think you're a nut. Personally, the moment I read the words "window seat" in your first posting I understood the feeling exactly. I have experienced panic attacks from claustrophobia, and for this reason, I will never, ever take a window seat. (I'm apparently the only person on the planet who will voluntarily choose a middle seat, if my only option is that or a window in a three-seat row. This is purely because the farther away I am from "freedom," i.e. the aisle, the more agitated I get.) If you're even vaguely claustrophobic, the experience of being confined in a window seat and unable to escape the aircraft itself could become unbearable very quickly.

As for the rational fear vs. irrational phobia question, the unfortunate fact is that a panic attack is utterly irrational, and yet completely impossible to reason away no matter how much you realize its senselessness even while it's happening. They are very terrifying just because of that issue. I'm a totally rational and analytical person normally, but when these things strike, there's absolutely nothing you can do about the physical effects. I personally feel like I'm about to suffer a heart attack. It's very scary.

My only remedy for impending panic attacks is to close my eyes and breathe very slowly and deeply, from the diaphragm, and just wait for them to subside.