The worst in-flight experience I have ever had was during a 24h-flight from Frankfurt to Melbourne. Could you imagine a crappy Alitalia 747 with 10 hours of straight turbulences? You don't want to, trust me. The worst thing was that I sat right at the wings and could clearly see the tip of the wing flexing with an amplitude of about 3 feet. I am thankful that those things flex that much. Otherwise we would have been toast.
