Anyone who has ever travelled in an airplane has to have looked out of the window at the magnificent view outside. And while looking out, it is near impossible for one to miss the small ‘hole’ close to the bottom of the window.
For the paranoid flyers, I am guessing the little hole might be scary, creating a sense of insecurity about whether the window’s going to crack any second. Well, they couldn’t be further from the truth.
The hole is there to maintain air pressure. And the hole, in fact, prevents the window from bursting.
The average airplane window has three panes: the outer and the middle panes are structural, keeping the difference in pressure in mind while the inner pane is present as a fail safe. The hole is located on the middle pane.
The pressure at 35,000 feet is about 1.5 kg per inch.
That is too low for the human body to stay conscious, therefore a cabin pressure of about 3.5 kg per inch is maintained.
The little hole helps equilibrate the pressure between the cabin and the air between the outer and middle pane.
It’s required for the outer pane to bear a maximum amount of pressure in case the fail safe pane is required in an emergency.