Why Airplane Windows Have Tiny Holes?

People traveling in a plane for the first time usually prefer the window seat, as it provides a grand view of the earth below. And as we are looking through the window, we tend to notice the small hole at the bottom. It makes us wonder what the tiny hole is doing there. For some, it can also be scary, as we have seen in movies that things tend to fly off from a plane when there’s a breach in the cabin. So, why does this tiny hole does not create the same effect? Well, to understand that, let’s a look at why airplane windows have tiny holes.

Understanding atmospheric pressure

At sea level, the atmospheric pressure is around 14.6 pounds per square inch or approximately 1 kg per square centimeter. This is what we are accustomed to and can breathe easily in this environment. However, at higher altitudes, the atmospheric pressure drops and there’s less oxygen in the air. This is why we experience breathing issues when we are in a high altitude region or climb a high mountain.

Airplanes fly at around 35,000 feet, where atmospheric pressure drops to around 3.4 pounds per square inch or 0.2 kilogram per square centimeter. At this altitude, we won’t be able to breathe and will die from lack of oxygen. Thankfully, airplanes have powerful ACs that increase cabin pressure, making it equivalent to the atmospheric pressure on the ground. This is why we are able to breathe easily inside a plane.

Why airplane windows have tiny holes

It’s clear from above facts that there’s a huge difference between outside air pressure and the pressure inside the airplane cabin. The entire plane has to go through significant stress to bear this difference in pressure. There are usually no issues, as planes are built using high quality materials. The windows are also made using toughened glass and other composite materials that can withstand the forces of a pressurized cabin.

The windows are usually made of three layers, an outer layer, a middle layer and the passenger side layer that you can touch. Most of the pressure is handled by the outermost layer and the middle layer is just there as an additional safety feature. The tiny hole you see is actually in the middle layer, although it may seem that it extends all the way to the outside.

The hole is there to achieve equal pressure between the outermost layer and the innermost layer. This allows most of the pressure to be exerted on the outermost layer and not the middle layer. It also helps in gradual increase and decrease in pressure exerted on the outermost layer while the aircraft climbs and lands.

Another function of the tiny hole in airplane window is to prevent fogging between the layers. If it wasn’t for the tiny hole, you may not have been able to enjoy the view outside. So, you see, it may be a tiny hole, but it performs some very important functions inside the plane.