People don’t understand basic airplane etiquette anymore.

Simple rules about polite behavior show that you’re considerate of other passengers and don’t ruin an entire flight for someone else.

For example, the person in the middle seat gets both armrests; the people in the window and aisle seats get only the one farthest from the middle seat.

Also, it’s rude to lean your seat back without getting permission from the person behind you.

Sure, you have the right to lean your seat back because you bought a ticket. But you’ll inconvenience and possibly hurt the person behind you.

Are you such a precious snowflake that you’ll make someone else uncomfortable just for your own comfort? It’s just selfish and rude and proves your parents raised you poorly.

Other than the grocery cart test (i.e. do you return your cart to the corral or abandon it in the parking lot, like a monster?), this is one of the signs of whether you’re a good person or not.

I once lodged a large water bottle into the seat pocket to stop someone from leaning back. (It only worked a little.)

And I have considered getting the Knee Defender, a device that blocks people from leaning their seats back. Or you can turn your fan on full-blast and point it at their head, except this might make them more comfortable in warm weather.

The entitlement of some people on airplanes these days is staggering.

I’ve read several stories about people who ask others to switch from their first-class seats to economy seats because of their own poor planning.

I saw a story this week about a woman who had upgraded her ticket to first class when a flight attendant asked if she would switch with a child seated in economy.

The kid’s parents had purchased first-class seats for themselves, but not for their kid, and were hoping someone would switch with the kid. The woman was asked to give up her seat for the kid. She rightfully declined, and the flight attendant said she was entitled to say no.

The parents gave her the stink eye during the duration of her very comfortable flight.

Once, on one of my flights, I had purchased a seat in Economy-Plus. I always pay for upgrades because I want an aisle seat that doesn’t have another seat crammed against my knees.

There were two girls in the two seats next to me, and their grandmother was across the aisle, in the window seat. Not a big deal — I was going to read, and it was only a four-hour flight.

But, no, Grandma was in a panic because she was not seated next to her granddaughters, so she asked me if I would trade seats with her.

“No,” I said. “I don’t like window seats.”

“But I want to sit with my granddaughters,” she said.

“Yes, but I paid extra to pick an aisle seat. I don’t want to give that up.”

“Why don’t you sit in this seat?” she said, pointing to the empty aisle seat next to her. This plane had three seats on one side and two on the other.

“Because that’s not my seat. Someone else upgraded to sit there, so I can’t just take it.”

“But how can I sit with my granddaughters?” she whined again.

“I don’t know. You should have thought of that when you bought the tickets.”

Was I being a jerk? Possibly. But I paid extra to be able to select that very seat. In fact, you’re allowed to choose your seats when you buy your tickets. Apparently, Grandma had not done that.

I returned to my book and waited for the plane to depart. Meanwhile, Grandma complained to a flight attendant that the mean man wouldn’t let her sit with her granddaughters.

“He doesn’t have to move,” the flight attendant told her.

No joy for Grandma because I was not going to move.

Just then, the woman who had the open aisle seat boarded so the grandmother explained her predicament. She asked if the woman would please switch seats so she could then switch seats with me and I could take the other aisle seat.

Luckily for Grandma, the woman agreed, so we made the three-way switch. I ended up across the aisle, and Grandma learned an important lesson about planning ahead.

It was a worthwhile switch. The woman and I had a nice time chatting about how entitled people are and how they expect that others will cover for their own poor planning.

The next time you buy airline tickets, remember that you have the option of choosing your seats in advance. Otherwise, airlines will just stick you in some random seat. They don’t care if you’re traveling with family members or not. Some airlines even charge for the ability to choose seats that are close together.

The families who don’t choose their seats find out the hard way that they aren’t able to sit with their kids. So, instead, they try to guilt some poor schmuck into switching with little Aubrey or Bailey and cram themselves into a middle seat.

Don’t let it be you. When you buy your tickets, pick your seat online, check in 24 hours in advance, and don’t let anyone guilt you into giving up your seat.

Unless they’ll put you in first class.