Which common airspace control measure involves using different altitudes?

The correct choice of vertical as the common airspace control measure that involves using different altitudes refers to the practice of managing aircraft operations by assigning specific altitude levels to various flight paths or types of aircraft. By doing so, airspace users can minimize the risk of collisions and ensure a structured flow of air traffic.

Vertical measures are particularly vital in ensuring that aircraft maintain safe separation from one another, especially in congested airspace or when different classes of airspace are in use. This altitude-based separation allows for more efficient use of airspace, enabling multiple aircraft to operate simultaneously without interfering with one another.

In contrast, lateral measures would involve horizontal separation based on position along the ground or flight paths at the same altitude, while timed measures would focus on scheduling aircraft movements to maintain safe spacing in a time-based manner. Horizontal refers to the lateral aspects of movement and does not specifically encompass different altitudes. Therefore, the concept of vertical separation is integral to aviation safety and operational efficiency, highlighting the importance of altitude differentiation in airspace management.