Why there are tiny holes at the bottom of windows on planes


If you've ever been on a plane, chances are, you've probably looked out your window, only to notice a tiny hole at the bottom of the "glass".

This seemingly random feature may not consume the thoughts of frequent fliers. But when you're speeding at 40,000 feet in the air, anxious fliers (we get you) might be bothered by this miniature hole. So, for all the nervous (and curious) travelers out there, we're here to debunk some of these all-consuming fears.

Plane window close up.
Plane window close up.

Photo: Getty

No, the glass isn't going to start breaking. No, you're not going to get sucked through the window like some movies have suggested. And yes, every window on the plane shares the same minuscule hole.

The breather hole, or a bleeder hole, as some call it, wears a few hats. To understand how it works, firstly, it's important to first understand how the window is engineered.

Composed of "acrylic materials", the window of the plane has three panes. There is an outer pane, middle and inner pane, or the "scratch plane". The breather hole is drilled into the middle pane. And along with the outer pane, the middle pane is one of the two most important layers of the window, according to Slate.

This video details the three panes:

When the plane takes off, the air pressure in the cabin and outside of the plane drops. In order to be able to breathe, the pressure inside the cabin must be maintained. Therefore, the hole is "used to regulate the amount of pressure that passes between the window's inner and outer panes".

According to Travel and Leisure, the breather hole is there to make sure the outer pane "bears" most of the pressure. In the unlikely case something happens, the outer pane would be the one to give out. And so, the passengers aboard the plane would still be able to breathe.

The second of the hole's uses is to keep the window free of fog, condensation and other things that may impact visibility. By allowing warm air to infiltrate in between the two panes, the breather hole ensures the plane is ready for any type of climate.

Cool, right?

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