Ever Wondered What That Little Hole in an Airplane Window is for? Well, it’s So Much More Important Than You Thought.

Travel by plane and the most you do is shuffle to your seat, kill time during the flight with work, a nap, or staring out the window, and then leave. The inner workings and details of the plane may not even register.

This GeoBeats video points out one of those details that helps a plane to function safely. Window seat fans might have noticed a tiny hole in the glass. What’s called a breather hole (or bleed hole) sits on the bottom of the window and acts to equalize pressure.

Found in the middle pane of each three-pane window on a plane, the holes have two purposes. First, the pane that’s closest to you – the one that you can make finger art on – is there as protection for the other two layers.

In between the middle and outer window panes is a small air gap that allows pressure to enter the breather holes. It balances out the difference in pressure.

As the plane ascends, the pressure drops inside and outside the cabin. Stabilized by the aircraft’s pressurization system, the pressure inside is higher. The windows are built to handle the weight from the thinner air on the outside, particularly that outer pane. It’s supported by the breather hole in the middle one.

While the plane’s in flight, the outer pane bears the brunt of the air pressure from the sky. If there were some catastrophic event that caused the outer pane to fail, the middle pane (with its bleed hole) would act as backup and contain the issue.

How important is this? When you increase in altitude during a flight, less pressure in the cabin means less oxygen to breathe while flying. At those heights, it’s comparable to being on top of the world’s highest mountain, and is extremely difficult to breathe normally.

So compressed air is pumped into the plane through from the engine and is recirculated so we can breathe. It prevents flyers from passing out from lack of oxygen. It’s all about pressure.

The other function that breather holes serve is to keep frost and moisture at bay. When was the last time you saw a foggy glaze on your window? If it weren’t for the bleed holes, you wouldn’t be able to enjoy the view as you soar above the clouds.

One of the measures in place to prevent a catastrophe such as a window cracking is the shape of the glass. The curved edges on plane windows help to alleviate pressure exerted by outside air by spreading it out. Square edges concentrate the pressure on the sharp points, leading to a potential problem.

So, breather holes are part of a carefully crafted design that puts safety first, helping us to breathe while flying. That will give you something else to ponder the next time you take your seat. Now, would you prefer the window, middle, or aisle seat?

Did you know why those holes were there? Were you aware of the complex design of airplane windows? What part of the plane are you curious about?