Turbulence: what we know before you feel it
Why turbulence happens, how pilots and controllers find out where it is before you hit it, and why your seatbelt is the only thing you need to worry about.
The short answer
Turbulence is uneven moving air, caused by storms, jet streams, mountains or other aircraft. Pilots know about much of it in advance from forecasts and reports from aircraft ahead, and controllers help them change level or route to avoid it. It's uncomfortable, but aircraft are built for far worse. Keep your seatbelt fastened when you're seated.
The drinks trolley rattles. Your coffee jumps. The seatbelt sign pings on. What’s going on outside?
What turbulence is
Air moves like water: mostly smoothly, sometimes in eddies and waves. When an aircraft flies through air moving up and down unevenly, you feel bumps. The main causes:
- Storms and cumulus clouds: rising and sinking air inside and around them.
- Jet streams: fast rivers of wind high up. At their edges, the air shears and tumbles. This is clear-air turbulence, the kind you can’t see.
- Mountains: wind flowing over high ground makes waves that can reach cruising levels.
- Other aircraft: wake turbulence behind them, which is why we keep bigger gaps behind large aircraft.
How we know before you feel it
- Forecasts. Weather services publish charts showing where turbulence is likely. Crews study them before take-off.
- Pilot reports. Aircraft that hit turbulence report it on the radio. Controllers pass it on to the aircraft behind.
- Weather radar. Aircraft carry radar that shows storms ahead, so crews can steer around them.
When a crew asks for a different level to find smoother air, controllers try to fit it in. That’s why your aircraft might climb or descend in the middle of the cruise.
Is it dangerous?
Airliners are designed and tested for loads well beyond what turbulence normally produces. The real risk is to people who aren’t strapped in. Most turbulence injuries happen to passengers and crew who were standing or not wearing seatbelts.
So: when you’re seated, keep your belt loosely fastened, even when the sign is off.