Dimly recall from law school days that it's a public order offence; if you tried it in the terminal you'd be carted off by airport police and probably be arrested.
Of course, it would be quite interesting to see how the cabin crew would handle it if you waited until airborne before disrobing... (I am, of course, not encouraging this).
(I can't access Tightslot's link; forgive me if i've missed something material as a result).
[Edited to add: this is in fact a response to stewmath's post, which now mysteriously appears below mine].