What actions should be taken when temperature is below 5 degrees Celsius?

When the temperature is below 5 degrees Celsius, activating the engine anti-ice is essential to ensure safe operations. At lower temperatures, there is an increased risk of ice accumulation on engine components, particularly in conditions where moisture is present. Ice formation can disrupt airflow and reduce engine efficiency, leading to potential power loss. By activating the anti-ice systems, pilots can prevent ice from forming and ensure that the engines operate properly.

In colder temperatures, altitude changes may not sufficiently address the potential for ice, and reducing speed doesn't directly mitigate the risk of ice accumulation on the engines. Landing immediately may be considered under more severe conditions but is not a necessary action solely based on temperature. Thus, activating engine anti-ice systems is the most appropriate response to safeguard aircraft performance and safety in cold weather.