Three weather - related deaths since January , FAA says . At least two of the three were victims not wearing seat belts . Turbulence is caused by quick changes in air movement . Air movements from ` ` clear - air '' turbulence are hard to detect .
Three turbulence-related deaths since 1980 , FAA says . At least two of the three were people not wearing seat belts . Turbulence is caused by quick changes in air movement . Air pockets from `` clear-air '' turbulence are hard to detect .