Scheduled to enter into service late next year, Boeing's 787 Dreamliner, like any other commercial aircraft, must be able to withstand 1.5 times the stress it could experience in flight. AirShowFan writes in:
Basically ... the airplane could be put through roller-coaster-like G forces and not snap. Of course us structural engineers will show some calculations and computer models to claim the structure can take it, but the FAA wants real undeniable proof. So whenever Boeing designs an all new airplane - something that only happens once every 10 or 15 years - we must test the wings to destruction.
Of course, this just means that 1.5000001 times the stress it could experience in flight is where the science starts being fun.
AirShowFan also directs us to the spectacular tests conducted on the 777: "You can see that the wing bends up a good 20 or 30 feet before it snaps - which should make you feel safe next time you look out the window at turbulent skies and see the wingtip moving up and down just a few feet."
If it doesn't creep you out to see the wing of a jetliner flexed up like a ruler on the edge of a desk, you're a nutter.