Well, we run all over town armed. I drive up and down I-75 armed. I am armed at home, at the mall sometimes, in crowded and lonely situations. Is being armed in a plane inherently different from any other crowded situation?
I suppose some extra training on just what not to hit (besides other innocents, of course) might be necessary, since a plane does have some additional vulnerabilities. But otherwise, the situation isn't all that different from carrying at the local mall.