Ever been in a plane and wondered why the flight attendants politely asked you to raise your window shades during takeoff and landing? With all of the frustrations that come along with modern air travel, we bet that this was the last thing on your mind!

But what you don’t know is, by performing this small action, you were actually doing your part in ensuring the safety of your fellow passengers.

You see, the airlines don’t ask travelers to do this just to annoy them – they already know plenty of other ways to do that! – they do it because it is one of the many necessary security precautions that are used during the flight.

According to LifeHacker, flight attendants ask passengers to raise those shades in case an emergency were to occur. Since most accidents tend to happen when the plane ascends and descends, the idea here is that the cabin crew would have an accurate visual cue if something were to go wrong. Theoretically, this could help with the evacuation process.

Saran Udayakumar, an aviation safety officer, asserts that this practice is a critical part of the flight—it allows for the crew to use their best judgement as to which side the passengers should disembark during an emergency.

The visibility is so important because—get this—the cabin crew only has 90 SECONDS to get everyone off of the plane if something were to go wrong. Now, that is not a lot of time!

In addition to it aiding in quick decision making, Udayakumar says that the method also helps to make all on board aware of possible complications. She writes:

Passengers are curious, hence they are perfect extra eyes to see if something goes wrong out there. Usually passengers report stuff right away.

We bet you didn’t know that the crew was counting on you to report issues as well, did you?

This rule has people draw parallels to tray tables and seat backs being put up during takeoff and landing, but, interestingly enough, it seems that up until recently not all airlines were following the procedure. It’s good to know that carriers are starting to adopt this system more widely these days!

Now, if you’ve ever had the pleasure of flying the Boeing’s super luxurious 787 Dreamliner, then you may be asking yourself: What do passengers do if there are NO shades to pull down in the first place?

For those of you who don’t know, these special planes don’t have physical shades over the window—they come equipped with glass that can be darkened by the passenger with just a click of the button.

Actually, in this particular scenario, the flight attendants’ job becomes much easier, as they have control over a master switch which allows them to lighten (or darken) all of the windows at once. How cool is that?!

To learn even more about this little-known nugget of air travel wisdom, be sure to read LifeHacker’s article here. I don’t know about you, but I’m certainly going to keep my eyes on that window during takeoff and landing from now on!

What do you think of this curious safety precaution? Have you ever experienced an emergency in the air? Tell us all about your thoughts and experiences in the comments section below!