I was on BA 289 a few months ago - as soon as we started to fly over Greenland the plane started to shake VERY violently. I was in F - my teapot jumped skyward off the ledge and I had to catch it! Then a glass of water dumped and ran down the entire window ledge. The same thing occured once we left Greenland.

Also, I was once in a Texas thunderstorm while in a Raytheon business jet. Its a good thing that little jet had shoulder belts because otherwise I could've broken my neck on the ceiling!