What Happens If An Airplane Window Breaks During A Flight?

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A shattered window is not rare in everyday situations, as windows crack all the time due to impact or sudden temperature changes. A broken office or home window can cause minor discomfort, allowing outside air to seep in and turning the insulation inefficient. However, a shattered airplane window can be a fatal risk for people on board due to rapid cabin depressurization.

That said, airplane windows are much stronger than regular home or office window panes with three layers of material. The multiple layers are part of the long list of redundant safety features (including opening the window shades during takeoff and landing) that keep the airplane secure even if some of the layers shatter mid-flight. Additionally, airplane windows have a tiny hole in the middle layer that adds to the window’s structural integrity. So, why do airplane windows need to be built so rigidly, and how can a shattered window turn into an emergency on an aircraft?

Airplane windows are built strong to withstand a huge pressure difference

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Airplane windows are extremely durable, built with multiple layers of redundancies for additional safety. This is because the windows play a crucial role in keeping the airplane pressurized while cruising at high altitudes.

If you have ever gone diving underwater, you know the weight of water feels heavier as you go down. That’s because more water is pushing you down, applying greater pressure. Similar to water, the air in the atmosphere applies a pressure on everything, including humans, animals, buildings, and more. As you climb up, the weight of air pushing against you decreases, resulting in lower air pressure.

Humans are accustomed to living comfortably under the atmospheric pressure at ground level. Though we can sustain a slight difference in atmospheric pressure, breathing in low air pressure can cause a variety of temporary and permanent health problems. Airplanes create an artificial pressure inside the cabin through a pressurization process to keep things comfortable for people on board.

To correctly pressurize the airplane, the cabin needs to be sealed from the outside air. The pressure inside the cabin is gradually increased as the plane climbs; however, this also exerts an enormous force on the airplane windows. The multi-paned approach makes windows safe to use under such pressure without shattering.

Shattered airplane windows can cause cabin depressurization

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The innermost layer on an airplane window restricts passengers from directly touching the two glass panes. Additionally, the middle layer takes charge if the outer layer shatters accidentally. Shattering of both the outer and middle glass layers is a rare phenomenon, but it has happened previously on flights like the Southwest 1380, resulting in the death of a passenger. In case both the glass layers shatter when the plane is cruising at some altitude, the airplane can experience rapid cabin depressurization.

Remember how airplane cabins need to be sealed from the outside air to remain pressurized. The breaking of an airplane window can expose the cabin to outside air, causing a sudden loss of cabin pressure. Apart from broken windows, faulty doors (like on the Boeing 737 MAX 9), or any other structural deformity that exposes the cabin to outside air can result in cabin depressurization.

The low pressure results in lower oxygen content in the air, causing a variety of health problems like dizziness and hypoxia, especially at higher altitudes. The oxygen mask mentioned during the pre-flight safety briefing deploys for each passenger in case of depressurization. The low oxygen content at cruising altitudes allows only one to three minutes of consciousness before most people lose the ability to think and act normally. The oxygen masks make it easier for passengers to breathe and allow pilots to descend to safe altitudes with a richer oxygen supply and tolerable air pressure.