What does "vertical separation" ensure in ATC operations?

Vertical separation ensures a minimum vertical distance between aircraft during flight. This concept is critical in air traffic control (ATC) because it maintains safe distances between aircraft operating at different altitudes, thus reducing the risk of mid-air collisions. By enforcing this vertical separation, air traffic controllers can safely manage multiple aircraft within their airspace, ensuring that, for example, one airplane flying at 10,000 feet does not encroach upon the airspace of another aircraft at 9,000 feet or 11,000 feet.

This minimum vertical distance, often specified in thousands of feet, allows for efficient use of airspace and enhances safety. It is particularly important in crowded airspaces where the lateral separation might not be sufficient due to the proximity of flight paths. Consequently, vertical separation contributes significantly to air traffic safety and operational efficiency.