What is clear-air turbulence and why is it so dangerous for pilots?

Clear-air turbulence is a growing concern for the aviation industry, with changing weather patterns potentially making encounters more frequent and severe.

Unlike storm-related turbulence, it can strike without warning, even when the sky appears completely clear.

What is clear-air turbulence?

Clear-air turbulence (CAT) is turbulence that occurs in cloudless skies and cannot be detected by conventional onboard weather radar.

Typically found at cruising altitude, clear-air turbulence (CAT) is closely linked to jet streams and sudden changes in wind speed and direction. These variations, known as wind shear, can disrupt airflow around an aircraft, causing sudden and sometimes violent movements.

Can pilots detect clear-air turbulence?

Weather radar is an essential tool, helping crews identify precipitation and steer clear of thunderstorms. However, it cannot directly detect clear-air turbulence, leaving flight crews reliant on other sources of information.

Weather forecasts, reports from nearby aircraft and updates from air traffic control all help pilots assess conditions along their route. However, the information is not always timely or accurate enough to prevent an encounter.

Atmospheric conditions can change quickly, meaning a report from another aircraft may no longer reflect what is happening when the next flight passes through. This makes it harder for pilots to plan their routes and avoid affected areas.

How is climate change increasing the risk of severe turbulence?

Research from the University of Reading suggests climate change is contributing to an increase in clear-air turbulence. A 2023 study examining atmospheric conditions between 1979 and 2020 found that, over an average point in the North Atlantic, the annual duration of severe turbulence increased by 55%. Moderate and light turbulence also rose by 37% and 17% respectively.

These changes are associated with shifts in atmospheric temperatures and wind patterns. As the planet warms, differences in temperature between regions can affect jet stream strength and behaviour, potentially creating greater wind shear.

This has particular implications for long-haul operators, whose aircraft regularly fly through major jet stream corridors. Understanding how these patterns are changing will be important when planning routes and assessing potential hazards.

How dangerous is clear-air turbulence?

Although commercial aircraft are designed to withstand considerable aerodynamic forces, passengers and cabin crew are more exposed to injury during sudden movements. Anyone not wearing a seatbelt can be thrown from their seat, potentially suffering serious injuries.

These dangers were highlighted by Singapore Airlines flight SQ321 in May 2024. The Boeing 777 encountered severe turbulence while travelling from London to Singapore, resulting in one passenger fatality and numerous injuries.

For pilots, incidents like this show the importance of cabin safety alongside aircraft handling. Crews may suspend meal services, ask passengers to return to their seats and request a different flight level when needed.

How do airlines predict turbulence?

Better information could help pilots make more informed decisions before reaching areas of unstable air. IATA’s Turbulence Aware platform is one example, sharing turbulence reports from participating aircraft with other operators. This gives flight crews and airline operations teams a broader picture of conditions along their routes.

Researchers are also exploring lidar technology, which uses laser pulses to detect changes in atmospheric density ahead of an aircraft. Although it is not yet a standard solution for commercial fleets, it could eventually provide pilots with an extra way of identifying hazardous conditions.

For the time being, improved forecasting, aircraft-to-aircraft data sharing and established cockpit procedures are central to managing the risk.

What does the future hold for turbulence and flight safety?

By its nature, clear-air turbulence is difficult to predict and there will always be situations where pilots have little opportunity to avoid it. However, better access to atmospheric data and advances in detection technology could give crews more time to respond.

As the aviation industry adapts to changing atmospheric conditions, improving its ability to forecast and manage clear-air turbulence will remain an important part of protecting passengers and crews.