I laugh at people who laugh at people who drink cran-apple on planes
Seriously, there's a method to the dumbness.
See, in airplanes, the air is very dry and people tend to get dehydrated. Caffinated drinks also help dehydrate you, so any non-caffinated drink is better than a caffinated one in an airplane, even if it is just sugar water.
However, it's also known that cranberry juice has known anti-infection properties, and is better than just taking vitamin C alone. A common ailment that travellers get after flying is... urinary tract infections, and cranberry juice clears those suckers up about as fast as antibiotics if you catch them early enough. If you don't stop them soon enough, the infections hurt like hell and they often come after being dehydrated and exposed to a change in environment (new place, new people, new bacteria your body doesn't know how to deal with yet) (edit: no, not THOSE kinds of bacteria or bugs... sicko). So, cranberry juice works 2 ways - it helps keep you hydrated, and it can help fight illness.
So I laugh at your laughing.