Clam chowder is not only stinky, it's potentially messy, making it a double faux pas. Natkin says that when you bring messy food on a plane, "You can pretty much count on getting bumped and jostled; your nice shirt will end up wrecked and you'll end up sitting there feeling sloppy for four hours." Or, worse, you can spill on other travelers.
Even fruit can be problematic. Rosenberg hates "when you're sitting next to someone and they're eating something really juicy or messy [like a] juicy orange and it's dripping and they're slurping and dropping orange peels on your lap." Battista warns travelers against cheese puffs. "There just aren't enough napkins."
Koh says, "Many travelers have no idea how to eat in a compact space. The number of times I have been elbowed by people who cannot eat with their elbows down and tucked within their allocated space is insane."
And don't forget cleanup. "Put your sandwiches (and all food you bring) in a zip-lock bag! It helps contain the mess and the trash later," Rosenberg suggests.