Extreme turbulence is rare — but when it happens, it makes news. Here's what 'extreme' actually means in aviation, what happens to the aircraft and passengers, and how common it really is.
Aviation uses a four-level scale: Light, Moderate, Severe, and Extreme. Extreme turbulence is the highest category, defined as turbulence that causes the aircraft to be violently tossed about and is practically impossible to control. Measured in EDR (Eddy Dissipation Rate), extreme turbulence exceeds 0.7–0.8 EDR — a level that is rarely recorded. For reference, moderate turbulence (common on transatlantic routes) is 0.2–0.4 EDR, and severe is 0.4–0.7 EDR. On most commercial routes, extreme turbulence events are encountered perhaps once every several thousand flight hours. When they do occur, the combination of suddenness and intensity means unsecured passengers and objects become projectiles.
The majority of serious turbulence injuries involve passengers who were not wearing seatbelts when turbulence struck suddenly. The physics are straightforward: at cruising altitude, a sudden updraft or downdraft can displace the aircraft several meters in a fraction of a second. An unbelted passenger maintains their momentum while the aircraft floor drops away beneath them — they become airborne, then impact the ceiling or overhead bins. The FAA reports 30–50 serious turbulence injuries to airline passengers annually in the US alone, with the number rising globally as air travel increases. Crew members, who move through the cabin without seatbelts, are disproportionately represented in turbulence injury statistics.
On May 21, 2024, Singapore Airlines Flight SQ321 (London Heathrow to Singapore Changi) encountered severe-to-extreme turbulence over Myanmar at 37,000 feet, caused by rapid convective development. The Boeing 777-300ER dropped suddenly — altitude loss of approximately 1,800 feet in under two minutes. One passenger (73-year-old British man) died from a suspected heart attack during or immediately after the event; 104 passengers and crew were injured, 30 seriously. The accident highlighted that even brief severe turbulence events at altitude can cause life-threatening injuries to unbelted passengers. The AAIB investigation noted the aircraft encountered conditions beyond what the weather radar showed, consistent with convective overshoot and clear-air outflow turbulence.
The single most effective protective measure is wearing your seatbelt whenever you are seated. Airlines instruct passengers to keep the seatbelt fastened when seated throughout the flight for exactly this reason — extreme turbulence gives no warning. Keep the buckle visible above your blanket so cabin crew can confirm it is fastened during checks. Avoid placing heavy items in overhead bins above your head — in severe turbulence, bin latches can fail. If turbulence begins, do not stand or attempt to reach the overhead bin. If you are in the aisle, hold a seatback and lower yourself to the floor until you can safely reach a seat. Crew training specifically covers turbulence procedures for these scenarios.
Ranked by historical turbulence score — click any route for details