1. Hog the overhead bin
Thanks to checked-baggage fees, space for carry-on luggage is at a premium. Which means that, sorry, no, your jacket doesn't get its own little area up there. Neither does your tiny purse. Nor your baseball cap. You do realize your selfishness is delaying takeoff because you've forced other people to spend time moving things around, right? Keep smaller items on you, and if there is room after everyone has boarded, then go ahead and stuff them in. Otherwise, under the seat they go.
2. Create noise pollution
Do not make people listen to whatever it is you're doing on your electronic device. It doesn't matter how low you have the volume: No one wants to spend three hours listening to random movie dialogue or the dings of a video game. Unfortunately this crime against fellow travellers is on the rise as more airlines switch to entertainment apps that require passengers to use their own devices. If you forgot your headphones, learn from your mistake and buy a pair from the flight attendant.
3. Be gross
This covers a range of acts, including but not limited to: going barefoot (and, even worse, going barefoot to the bathroom), stuffing used banana peels and apple cores in the seatback pocket, cleaning out your ear wax while sitting next to stranger, chewing with your mouth open and clipping your nails. (If you're reading this thinking, "Oh come on, people don't do those things," then you are wrong, my friend. Dead wrong).
4. Disrespect the book
Listen, I get it: You're a nervous flyer and need some reassurance. Or you're a mom longing to talk to a sane adult after a week on a Disney cruise with your family. You still need to take the hint: If the desired target of your banter is reading a book – or, more blatantly, has headphones on – he or she doesn't want to chit-chat. With anyone. It's not personal, really.
5. Sing out loud
You would think some things wouldn't need to be said. Yet on a recent flight to New York the lady across the aisle from me spent much of the flight performing in her own one-woman karaoke bar, singing along to the music playing in her headphones. The fact that I had my laptop out and was clearly trying to work made this even more irritating. Unless people regularly pay big bucks to hear you perform, keep that urge to belt it out bottled up.