Another source of stress is that planes make noises, especially during take off and landing cycles, like flap movements landing gear up and down etc. There are all normal and you need to expect these. Turbulence is another worry for some, again to be expected and do not worry about these movements. If you want to watch, there is a video clip about Boeing stress testing the wings, should allay any fear, although did horrify me when I saw what they did to the nice plane:shock:. Google it, its pretty common.