There are a few things that fellow travelers in a commercial airline frequently do that are inconsiderate of other passengers and could easily be avoided. These things may not bug everyone, but with millions of miles logged on many carriers across many countries, I’ve not yet come to peace with them.
1) Bringing warm food to eat when others are not eating
Warm food smells sort of gross when it is not yours! The aroma of a hot pizza slice or a greasy burger may smell good to you if you are about to eat it, but for everyone else around you, it smells funky. Aromas like that fill the airplane cabin quickly, and are especially noticeable when it is just one person chowing down. To others, the odor is for something you are about to eat, and will not be sharing with them. Also, if the smell is a meat smell, which it often is, any vegetarians on the plane (of which I am not one) are being forced to smell you eat an animal. If it is just not possible to eat what is served to everyone else, bring cold snacks like nuts, a granola bar, or a cookie. If you do bring hot food, keep it sealed up until the flight attendants serve food – on international flights, the food they serve is also aromatic and yours will mix right in. On domestic flights, sometimes the only thing people are served is a drink – but even drinks have an aroma for people and will help mask your faux pas.
2) Using the chair back in front of you to support yourself when getting in or out of your seat
The chair back in front of you looks oh so convenient to grab a hold of to counterbalance your torso as you wiggle yourself out of your seat. After all, it is almost impossible to get out of a middle or window seat by just standing up and walking out – your torso and head are typically canted back over your seat, making your center of mass always imbalanced. However, in that situation, instead of pulling on the seat back in front of you, push on your own seat back to keep your balance. Pulling on the seat back in front of you jostles the passenger in that seat. The larger the person trying to leave their seat, the more difficult the maneuver is (due to tight space), and often the more violent the jostling of the passenger in front.
3) Trying to exit the aircraft without allowing the seats in front of you to empty
The proper behavior for exiting an aircraft is, when the seat belt light is turned off, folks in the aisle seats get out and, as the line in front of them in the aisle clears out, they wait for passengers in the middle and window seats in the row ahead of them to exit. The faux pas is when people in the aisle barge past a row of people in front of them trying to exit into the aisle. This one is especially noticeable in Asia, and a constant reality in mainland China. There is some herd mentality there that makes people have a disregard for line etiquette.
Ok, that’s pretty much it! There are other airline faux pas, but most are either comparatively minor, more amusing than rude, or do not occur consistently.