Which description correctly defines lateral separation?

• A. It is the altitude difference between aircraft.
• B. It is the horizontal distance between aircraft.
• C. It is the time difference between aircraft.
• D. It is the same as vertical separation.

Answer: (B)

Lateral separation is the horizontal distance between aircraft. It describes how far apart two airplanes are on the map—the spacing in the plan view of their positions, not how high they are or when they pass by. So the description “the horizontal distance between aircraft” is the correct one. The altitude difference is vertical separation, and a time difference would be time separation, not lateral. In practice, controllers maintain a minimum horizontal (lateral) gap to keep aircraft safely apart on the same or adjacent routes.