From an airplane seat, you really don't get a good look at just how much plane wings can bend.
They're built to withstand the worst of weather, coupled with impromptu bouts of turbulence. As you probably assumed, airplanes are put through tons of tests to make sure each element is working perfectly before they hit the skies.
This is probably what you're used to seeing when it comes to airplane wing flexibility:
But the video at the top of the story showcasing an airplane fatigue test is a good look at just how much bend the wings really have. A fatigue test is when a plane is put through motions that would equal many more flights than any plane would actually take before retirement to make sure its static strength is solid. For example, a Boeing blog post from 1997 describes the strategy for one plane's fatigue tests:
"The Boeing 777 fatigue test airplane has lived up to its name and is in for a much-deserved rest after having 'flown' the equivalent of 120,000 flights. This represents 60 years of service, an unprecedented level of test validation for a new Boeing airplane model."
According to Wired, wings are often tested by stacking bags of sand on top of them to mimic the various forces that an airplane experiences while flying. For extended testing, cage-like structures are created around the airplane to force the wings upwards to see just where the breaking point is. You can see one of these structures in the first video.
Static testing is another important part of the wing designing process. Unlike a fatigue test, where a plane's wings are put to work, static testing has one goal: see just how far a wing can bend before it snaps. In the video below, you can actually see a wing snap, much to the surprise of the crowd of onlookers:
According to Popular Mechanics, the airplane in the video above reached 154 percent of its designed stress before cracking like a branch.
And, just for good measure, yet another stress test for you to enjoy:
Why do airplane wings bend so darn much? In short, the wings act as springs. If pressure is applied, they will attempt to spring back to their resting place, with flexibility. Wired broke down the science behind this intended bend, if you're looking to learn more about an airplane's wing oscillation (complete with diagrams and DIY experiments you can do at home).
So, hopefully this gives you some peace of mind the next time you're fretting your way through your flight. And if these videos don't, this image from Wired will.