What does a Red / denote on the aircraft forms?

A red slash or marking on aircraft forms typically indicates that there is a discrepancy pertaining to equipment. This visual cue is crucial for maintenance personnel and pilots as it signifies that there is an issue that needs addressing before or during operation. Such discrepancies can range from minor defects to more serious issues requiring immediate attention to ensure the aircraft’s safe and effective functioning.

The other options refer to different states of the aircraft or its equipment. For instance, indicating that an inspection is due signifies routine maintenance requirements, while labeling the aircraft as unsafe for flight suggests a more severe condition that could theoretically be indicated by other symbols or markings. Lastly, marking normal operation of equipment would usually be denoted differently, ensuring that each status is clearly communicated on the documentation.