Although I haven’t been in a plane for nearly two years, I still ruminate about proper travel etiquette, such as armrest access. This article from the website Jalopnik settles the ongoing arguement regarding equitable sharing of airliner armrests.

Here’s the straightforward explanation by seat:

Aisle

This seat gets the outside armrest only. The aisle seat enjoys free access to leave the row to use the bathroom, considerable stretching room on the aisle side, and the most open feel of the row.

The responsibilities of the aisle seat are to get up to allow your row-mates access to bathrooms or the rest of the aircraft.

Center

This seat gets the both armrests. The center seat has none of the benefits of the aisle or window, and as such is compensated with the use of both the armrests that border the seat.

It is generally agreed to be the worst seat in the row, and as such deserves the compensatory extra armrest.

Window

This seat gets the wall-side armrest. The window seat has, of course, the window, which reveals the miracle of heavier-than-air flight to those who are still capable of feeling such joys, hence why it’s the most popular seat choice for children. The wall also offers valuable lean-against-to-sleep options, and a modicum of privacy, if you push your face into the wall as you have a phone call or whatever.

The downsides are you’re just as trapped as the middle seat, and you may be asked to adjust the window shade, which you really should comply with if requested reasonably.