What does "moderate turbulence" actually mean?
Light, moderate, severe: the official FAA scale pilots use, in plain English, and what each level feels like from your seat.
In this article · 6 sections
Why there's an official scale
When pilots report turbulence, they use a standard scale published by the FAA, so a "moderate" report from one crew means the same thing to the next.1 Forecasters use the same words in turbulence forecasts.2 Knowing the scale takes a lot of the mystery out of a captain's announcement.
The levels, in plain English
These descriptions come from the FAA's Turbulence Reporting Criteria table.1
| Level | What the airplane does | What you feel in the cabin |
|---|---|---|
| Light | Brief, slight changes in altitude or attitude, or slight rhythmic bumpiness ("light chop") | A slight strain against your seat belt. Food service may continue, and walking is little or no trouble |
| Moderate | Like light, but stronger. Changes in altitude or attitude happen, but "the aircraft remains in positive control at all times" | Definite strain against your belt. Unsecured objects move. Walking and food service are difficult |
| Severe | Large, abrupt changes in altitude or attitude; the aircraft may be momentarily out of control | You're forced violently against your belt. Loose objects are tossed about. Walking is impossible |
| Extreme | Violently tossed about and practically impossible to control; may cause structural damage | The top of the scale. Forecasts and pilot reports exist so crews can plan around the worst areas2 |
Pilots also report how often it happens: occasional (less than a third of the time), intermittent (a third to two-thirds) and continuous (more than two-thirds).1
"Chop" vs "turbulence"
The scale separates chop, which is rapid, somewhat rhythmic bumpiness without noticeable changes in altitude or attitude, from turbulence, which does involve those changes.1 Moderate chop can feel like a gravel road; moderate turbulence feels more like a series of small lifts and drops.
Why "moderate" is less scary than it sounds
The word "moderate" sounds alarming when you're nervous, but look at the official definition again: the airplane stays in positive control the whole time.1 What changes is how comfortable it is to move around. That's why crews stop the service, sit down themselves and ask you to stay buckled.
What to do at any level: keep your seat belt buckled at all times when you're seated, even if the sign is off.3
See the forecast for your flight
The NWS Aviation Weather Center publishes turbulence forecasts using these terms.2 My Flight checks the official outlook and recent pilot reports along your route and translates them into plain English, with no scores.
Keep reading
Quick answers
What does moderate turbulence feel like?
You feel definite strain against your seat belt, loose objects can move, and walking and food service are difficult. The FAA definition says the aircraft remains in positive control at all times.
What is the difference between turbulence and chop?
Chop is rapid, somewhat rhythmic bumpiness without real changes in altitude or attitude. Turbulence involves changes in altitude or attitude, such as a sudden rise or a small roll.
Is moderate turbulence dangerous?
The official definition says the aircraft remains in positive control at all times. The risk is to people who aren't buckled in, which is why the FAA advises keeping your seat belt fastened whenever you're seated.
What do occasional, intermittent and continuous mean in a turbulence report?
Occasional means less than a third of the time, intermittent means a third to two-thirds, and continuous means more than two-thirds of the time.