I've flown through a thunderstorm in a relatively small plane (ATR-72)... severe turbulence for a while, maybe 15 minutes...

What's strange is I never really had a panic instinct. Never seemed like there was any real danger or that the plane was "falling apart".

It was mostly a lot of being violently jerked side to side or floating weightless for a few seconds followed by slamming back down. But nothing that sounded like pieces of the plane were stressed. Really most of the noise was everything in the galley slamming around and an occasional startled yelp from a passenger. And the sound of the engines a few times at full throttle trying to gain back some altitude.

Everyone was firmly buckled in, otherwise there easily could have been many broken bones. Now I am adamant about keeping the seat belt on all the time. I would have had a concussion without it.