A pilot has revealed the very important reason as to why plane windows have a tiny hole in them. Despite flying becoming a very normal part of many of our lives, there are still so many things we don't understand about airplanes. And I'm not talking about all the complicated buttons found in the cockpit, I'm talking about the little things that are right in front of is as we fly. For example, that tiny little hole in the plane's windows. <img class="size-large wp-image-1263141465" src="https://img.vt.co/2022/01/ER0FWW-1024x683.jpg" alt="" width="1024" height="683" />[[imagecaption|| We've all seen it - but what's it for? Credit: Bart Pro / Alamy]] I'm sure it's something many of us have noticed and questioned. Why is there a tiny hole in my window and why is it slowly growing a snowflake around it? Well, it turns out that this hole is known as a breather hole or a bleed hole. The next time the inflight movie is failing to hold your attention, take a closer look at your window and you'll notice that it is made of three separate panes - commonly made of acrylic materials. The pane closest to you is known as <a href="https://thepointsguy.co.uk/news/what-are-airplane-windows-made-of/">the scratch pane</a> and its purpose is to protect the other panes. The outer pane is flush with the outside of the plane's fuselage and measures about 0.4" thick. This pane is there to "carry the pressure loads for the life of the window", says Jason Webb, Director of Business Development and Aftermarket Services at GKN. Speaking to <a href="https://thepointsguy.co.uk/news/what-are-airplane-windows-made-of/">ThePointsGuy</a>, Webb adds that the increased thickness is meant to “to allow for engagement with the airframe structure while maintaining the required strength." <img class="size-large wp-image-1263141466" src="https://img.vt.co/2022/01/2BER0PF-1024x681.jpg" alt="" width="1024" height="681" />[[imagecaption|| It turns out that little hole has a very important purpose. Credit: Jakub Rutkiewicz / Alamy]] Now, the most inner pane -  the one with the hole in it - measures about 0.2" thick and is there to serve as a fail-safe if the outer pane fails. The two most outer panes are the most important. As the plane climbs in altitude, the air pressure inside and outside the cabin starts to fall. As a result, the plane has a system in place to keep the pressure at a safe level and comfortable for passengers. Writing for <a href="https://slate.com/human-interest/2015/05/whats-that-thing-why-are-there-holes-in-airplane-windows.html">Slate</a>, pilot and author Mark Vanhoenacker explains: "This means that the pressure inside the aircraft during flight is typically much greater than the pressure outside. "The outer two cabin windows are designed to contain this difference in pressure between the cabin and the sky. "Both the middle and the outer panes are strong enough to withstand the difference on their own, but under normal circumstances, it's the outer pane that bears this pressure - thanks to the breather hole." Director of technology for GKN Aerospace Marlowe Moncur, further explains: "The purpose of the small bleed hole in the [middle] pane is to allow pressure to equilibrate between the passenger cabin and the air gap between the panes, so that the cabin pressure during flight is applied to only the outer pane." And that little hole also has another important function. Per <a href="https://www.thesun.co.uk/travel/17277588/plane-window-holes-explained-secret/">The Sun</a>, the bleed hole also allows for moisture to escape the fuselage, meaning fog won't form in the window and spoil your lovely Instagram shot. So there you have it. It's something we've all thought about - but now you know! Featured image credit: @dsokol66 / Alamy

Pilot explains why airplane windows have that tiny little hole in them

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