Tiny holes on Airplane windows and their Function


Especially frequently flying passengers have noticed the small hole at the bottom of windows of an aircraft. Ice crystals sometimes form around this hole when the aircraft is at cruise altitude.

Well, do you know what this little hole does?

This small gap, can be called a “bleed hole” or “breathing hole”. When you look carefully at the aircraft windows, you see three layers.

A plastic cover is actually placed on the innermost layer to protect the glass. The breathing hole is located on the middle layer. The third is the last layer in contact with the harsh weather conditions outside the aircraft.

Tiny holes on Airplane windows

What is the role of the holes on Airplane windows?

As it is known, the pressure in standard passenger aircraft cabinets is equivalent to the pressure at an altitude of 2,500 meters above sea level.

In B787 and A350 type aircrafts, which have been developed and put into service by Boeing and Airbus in recent years, this height has been reduced to 1,800 meters.

As the aircraft rises after take-off, the pressure begins to decrease both inside and outside the cabin. But the outside pressure is always much lower than the inside pressure at cruising.

The second and third layers in the planes’ windows are a durable interface between the external pressure and the internal pressure. And as we mentioned above, the most critical task in this difficult situation belongs the outermost layer.

*Let’s come to the function of the little hole in between… This hole ensures that the pressure    of the air in the cabin is balanced with the pressure of the air between the second and third layers.

*The hole has a second function. Moisture accumulated between the second and third layers is also evacuated through this hole, thereby preventing misting in the windows of the aircraft.

holes on Airplane windows


The ice crystals formed at the edges of the hole are formed as a result of the relatively hot air inside the cabin coming into contact with the window surface, which has cooled down.

After all, we can say that this hole which seems small and unnecessary, is actually has vital importance for the aircraft.

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