To ensure minimum vertical separation when pilots are not executing pilot's discretion descent, what should be assigned?

Assigning an altitude after climb or descent clearance is essential for ensuring minimum vertical separation, particularly when pilots are not executing a pilot's discretion descent. This approach allows air traffic controllers to maintain safe vertical spacing between aircraft by providing a clear, definitive altitude for pilots to aim for after they receive the appropriate clearance.

When controllers issue an altitude to be maintained after a climb or descent clearance, it establishes a firm guideline that pilots must follow, thus preventing any potential conflicts with other aircraft operating in the same airspace. This is crucial in maintaining safe operations, as vertical separation is a key component in preventing mid-air collisions.

In contrast, while altitude restrictions may provide some level of guidance, they do not offer the same clarity as a specific altitude to maintain following a clearance. Other options, such as assigning a specific heading or a direct approach clearance, do not directly address the need for ensuring vertical separation in the context of altitude management. Therefore, the assignment of a specific altitude after a clearance is the most effective and safety-oriented choice for achieving the necessary vertical separation.