Turbulence — Irregular air movement causing sudden changes in aircraft altitude or attitude.

Turbulence is irregular movement of air that results in sudden changes to the aircraft flight path. Turbulence is classified by intensity:

• Light: Slight, momentary changes in altitude/attitude
• Moderate: Definite changes, aircraft remains in control, unsecured objects displaced
• Severe: Large, abrupt changes, aircraft may momentarily be out of control
• Extreme: Practically impossible to control, structural damage possible

Types: convective (thunderstorms), mechanical (terrain/buildings), clear air turbulence (CAT, jet stream), wake turbulence (behind large aircraft), and mountain wave turbulence.