Turbulence is the most common reason passengers grip their armrests. Here’s what causes it, how dangerous it really is, and why scientists think it’s getting worse.
Turbulence is simply air that isn’t moving smoothly.
A plane flies through air the way a boat moves through water. When the air is calm, the ride is smooth. When the air is rising, falling or swirling unevenly, the plane is pushed around with it, and passengers feel bumps, drops and shakes.
There are a few main causes. Thunderstorms create strong up and down currents. Wind flowing over mountains can create waves in the air, much like water over rocks. Large aircraft leave swirling wake behind them. And high up, where jets cruise, fast-moving rivers of air called jet streams create turbulence where they rub against slower air around them.
That last type, known as clear-air turbulence, is the hardest to deal with. It happens in cloudless skies, isn’t picked up by weather radar, and often gives pilots little or no warning. Pilots rely on forecasts and reports from other aircraft to avoid the worst of it.
How dangerous it is, and why it’s increasing
For the aircraft itself, turbulence is rarely a serious threat. Modern passenger jets are designed and tested to withstand forces well beyond what even severe turbulence produces, and pilots slow down to reduce the strain.
The risk is mostly to people inside the cabin. Passengers and crew who aren’t strapped in can be thrown against the ceiling or into the aisle. In May 2024, a Singapore Airlines flight from London to Singapore hit severe turbulence and diverted to Bangkok. A 73-year-old passenger died and dozens of people were injured. Incidents like that are rare, but they are why airlines urge passengers to keep their seatbelt fastened whenever they are seated.
Scientists say the skies are getting bumpier. A study from the University of Reading found severe clear-air turbulence at a typical point over the North Atlantic, one of the world’s busiest flight paths, increased by 55% between 1979 and 2020.
The researchers link that to climate change. Warmer air is strengthening the difference in wind speeds within jet streams, known as wind shear, which creates clear-air turbulence. Some studies suggest severe turbulence could become two or three times more common later this century.
Airlines are responding with better forecasting tools and more data sharing between aircraft, so pilots can see bumpy air coming and steer around it.
