If you’re a window-seat kind of a person, you’ll be very familiar with the little crystallised holes on the outside of your plane window. And you’ve probably gone through a moment of panic — is there a hole in the window? Will it crack and break? Not to worry, the holes are there on purpose, to protect you.
But, how? Firstly, the window that you can touch is actually only one of three acrylic layers: the first pane, closest to you, the middle pane, which sports the main hole called the breather, and the outer pane. Now, planes fly between 36,000 and 40,000 feet in the air and at that height, the level of oxygen is very low. At sea level, the average human experiences just under 15 pounds of pressure per square inch, however, the higher above sea level we climb, the less pressure — 3.4 pounds in total to be exact — we feel.
In an effort to minimise the discomfort we feel, the plane has an air conditioner pump air into the plane similar to the pressure we feel on the ground. And while this is beneficial for us, it causes an imbalance — low pressure outside, high pressure inside — which the air inside the plane seeks to correct.
Pilot Mark Vanhoenacker, writing for Slate says: “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.”
Why switch on flight mode on a plane?
Flying in a giant metal object seems to encourage our deepest paranoias to really come out and air themselves like no other activity.
People who “look wrong”, WiFi spots that sound wrong, passengers who just are wrong — all have grounded highly expensive journeys via collective freaking-out. But if you put your phone in flight mode, you’re a bit safer, right? Not really. The radiation from a phone signal cannot interfere with the plane’s operating system to the extent that it will cause the whole thing to spontaneously combust. Even if lots of terrorists kept their phones on and watched data-zapping YouTube videos all at the same time. But leaving your phone on not in flight mode does mean you could give the pilot a headache.
Here’s what happens in about three per cent of cases when phones are left whirring away, according to a pilot on Quora: “You may have heard that unpleasant noise from an audio system, that occasionally happens when a mobile phone is nearby. I actually hear such noise on the radio while flying. It’s not safety critical, but annoying.”
Someone else described the noise. “It makes a bzzzt-bzzzt-bzzzt-bzzt-bzzt. Now imagine that noise in the pilot’s headphones, while (he or she) is receiving a critical bit of information from ground control!” So there we have it — no need to be paranoid, but it is definitely a common courtesy to hit that flight mode button.