Which type of signs denote areas where aircraft should not enter?

Mandatory signs are specifically designed to convey messages that require immediate compliance, particularly in aviation contexts where safety is paramount. These signs indicate areas where aircraft must not enter, such as restricted zones or active runways. The characteristics of mandatory signs typically include a red background with white characters or symbols, making them highly visible and unmistakable.

These signs play a crucial role in maintaining safety by ensuring that pilots and ground personnel are aware of and adhere to critical operational restrictions. Understanding the distinction between mandatory signs and other types of signs, such as information or location signs, is essential for proper adherence to airfield regulations and ensuring overall aviation safety. Information signs typically provide non-critical data, location signs help identify specific areas, and guidance signs assist with navigation but do not impose restrictions like mandatory signs do.