What are the three levels of turbulence that crew should be aware of?

The classification of turbulence into light, moderate, and severe is essential for flight crews to effectively communicate the conditions they may encounter while in the air. Light turbulence is characterized by slight, erratic changes in altitude and/or attitude of the aircraft, causing a slight strain against the seatbelts but not significantly affecting the aircraft’s flight path or handling. Moderate turbulence involves greater intensity, with noticeable changes in altitude and/or attitude and potential difficulty in controlling the aircraft, requiring crew to be more vigilant and possibly instructing passengers to remain seated with seatbelts fastened. Severe turbulence is marked by large, abrupt changes in altitude and/or attitude, leading to strong, sustained strain against seatbelts and possibly causing unsecured objects to be tossed around, discretion is advised as crew needs to ensure safety protocols are strictly followed.

The other classifications (low, medium, high; incidental, notable, extreme; minor, major, critical) do not conform to the recognized terminology used in aviation for describing turbulence levels, which is standardized to ensure that all aviation personnel operate on the same understanding of flight conditions.