A controller may issue a safety alert to an aircraft in what situation?

A controller issues a safety alert primarily when an aircraft is in unsafe proximity to terrain, obstructions, or other aircraft. This situation is critical because it directly pertains to the safety and operational integrity of the aircraft. Alerts are designed to provide timely warnings that allow pilots to take necessary corrective actions to avoid potential collisions, terrain impacts, or other hazardous situations that could jeopardize the safety of the flight. The emphasis on unsafe proximity ensures that controllers are proactive in safeguarding aircraft operations by monitoring and communicating vital information that could lead to an accident if not addressed.

While situations such as being low on fuel, experiencing adverse weather, or reporting an emergency are important for a controller to be aware of and might prompt communication, they do not specifically mandate a safety alert in the same urgent manner as a threat of collision or terrain proximity. Thus, the issuance of a safety alert is particularly focused on imminent risks that could directly result in an in-flight hazard if not dealt with promptly.