I have flown a lot for business. I have no fear of flying, it is very safe, However everything about it is stressful, getting to the airport is just the start. Travelling business class helps (can't comment on first class as I only got upgraded to first once).
It's all the hanging around, uncertainty, boredom etc that gets me.
I'm pretty sure that no plane has crashed due to turbulence, but it sure can be uncomfortable. Luckily I can sleep though most flights, my best flight was falling asleep in Hong Kong and waking up in Heathrow.