Being locked in a confined space with hundreds of strangers can bring out the worst in even the calmest of people.
So you'd be forgiven for getting easily irritated on a long haul flight.
But one female passenger on a flight to the US from Ireland has been deemed so rude she has managed to enrage thousands of people on the ground too.
Her offence? Eating pistachio nuts and chucking the shells on the floor.
The woman caught the attention of a fellow traveller on the flight, who took a snap and posted it on the online forum Reddit.
The post quickly attracted the ire of the internet, with people calling her "trash", a "slob" and "absolute scum".
"No matter how you rationalise it, she is a pig who belongs in a barn. You don't do this kind of thing on an aeroplane," Reddit user Bubbaganewsh wrote.
"This is a very good example of what is wrong with society today," another Reddit commenter, UseMoreHops, wrote.
A person who claimed to be an airline employee slammed the woman on behalf of all flight attendants.
"This pisses me off beyond belief. At my airline, flight crew are the ones that clean the planes between flights to save money. We are not paid on the ground, we do this for free," they wrote.
But the abuse didn't stop there.
"She probably wonders why she's not married or no one asks her out on dates. It's because you're a slob, in case you didn't know," shadynook1924 said.
"Some people are just slobs. Nothing you can do about them, because an over-inflated sense of entitlement tends to accompany it," CodeMonkey24 wrote.
And another person even bought her parents into it.
"She looks young, probably used to mummy or daddy cleaning up after her - a product of great parenting," dude_nyc claimed.
There were a minority which came to the passenger's defence, with one user called Paul02008 saying he didn't understand the big fuss.
"The aisles get vacuumed after every trip regardless, I don't see what the big deal is."
But in any case, that sure escalated quickly.