If you are a keen observer, you will have noticed that the moment the plane lifts off the ground and begins its flight, the wings curve upward. On some aircraft, this is quite subtle, but on larger planes, the wingtips can "rise" by several meters!
Once the airplane's weight is no longer supported by the wheels on the runway, it rests entirely on the wings. It is the wings, through the aerodynamic forces they generate, that support the aircraft and allow it to fly (see this post).
However, if the wings were rigid while being subjected to such immense stress, they would snap easily at the slightest turbulence. Their flexibility, on the other hand, allows them to withstand enormous forces without any problems.
Everything Bends
Just like the wings, all parts of an airplane have a certain degree of flexibility. Sometimes, if you are seated in the very last rows of the tail during heavy turbulence, you might see the entire cabin in front of you "oscillating" along its entire length... it’s not your imagination, it’s actually happening!
Similarly, if you look out the window and can see an engine, you might notice it "dangling" or swaying slightly as it hangs from the wing.
Ultimately, skyscrapers, bridges, spacecraft, and all large structures are designed with a certain level of flexibility to cope with extreme stress.
DontWorryFlyHappy!