Which of the following is a potential security breach sign at the airfield?

A sudden influx of unregistered visitors is a clear indicator of a potential security breach at the airfield. This situation raises concerns because unregistered visitors could pose risks, such as unauthorized access to restricted areas, theft, or other malicious activities. Airfields have strict security protocols in place to monitor who enters the premises, and any unexpected or unusual increase in visitors who have not been cleared for entry could signal a serious security concern that needs to be addressed.

In contrast, an aircraft with a mechanical issue is a common scenario in aviation and does not inherently indicate a security threat. Normal aviation activities reflect the regular operations at the airfield, which typically wouldn’t raise any alarms. Similarly, an increased staff presence is often a proactive measure for ensuring safety and security rather than a sign of a breach since it could be in response to scheduled events or operations. Thus, the presence of unregistered visitors stands out as a primary red flag in the context of airfield security.