The most horrific flight I ever experienced was on Air Jamaica. The devil baby behind me screamed piercingly, bloodcurdlingly, at the top of its lungs the entire way from Kingston to JFK while its mother calmly read a book, ignoring her progeny and her increasingly fractious fellow passengers. The coup de grâce was copious vomiting upon landing.
If I had to pick a setting for disgusting habits, though, it would be the gym locker room.
From Mile High Peg.