Under what conditions is a fuel jettison system required?

A fuel jettison system is essential in scenarios where the aircraft's maximum takeoff weight surpasses its maximum landing weight. This situation can arise when an aircraft takes off and later finds it necessary to return to the airport shortly after due to issues such as engine failure, inclement weather, or other emergencies.

In these instances, the aircraft may not be able to land safely at its current weight because it could exceed the maximum landing weight limits set by safety standards. Therefore, to mitigate the risk of structural damage or performance issues during landing, the fuel jettison system allows the crew to safely reduce the aircraft's weight by offloading fuel.

While other options present various flight conditions, none directly relate to the fundamental reason for requiring a jettison system, which is to ensure safe landing weight management.