In severe cases it can lead to damage to aircraft and injury for those onboard.
Flights are becoming more turbulent because of climate change.
Research by the University of Reading in the UK has found clear-air turbulence, which happens suddenly, has increased in a number of regions globally.
Warmer air from higher CO2 emissions is responsible.
In the North Atlantic, one of the worlds busiest flight routes, the duration of severe turbulence has increased by 55% between 1979 and 2020, moderate turbulence rose by 37%, and light turbulence was up 17%.
In severe cases it can lead to damage to aircraft and injury for those onboard.