common spot for what's called mountain wave turbulence. >> the turbulence caused by those mountains can reach well above the height of the mountains themselves and cause the air to tumble and roll and create turbulence. >> turbulence can also be triggered by thunderstorms, even when the skies are clear. >> convective turbulence is caused by rising hot air, typical everywhere, especially in the summertime when the ground is warm and hot air is rising. >> turbulence is very erratic, very spotty. so it could be that if they were at this very same location even ten minutes later, it may not have been a severe event. >> but that doesn't change things for the passengers of united flight 1676 who had a flight they will never forget. jennifer gray, cnn, atlanta. all right. when you think about atlanta, the capital of georgia, you might think of the world of coca-cola, the king center, and