When a CAT I is following a CAT III arrival, what runway separation is required?

• A. 1,000 ft separation
• B. On runway
• C. Clear of runway
• D. 500 ft separation

Answer: (C)

The situation hinges on how runway occupancy is managed when different instrument approach categories are lined up for the same runway. A CAT III approach is a precision, low-visibility arrival that often uses autopilot and requires a clear, unobstructed runway environment during landing and rollout. When a CAT I is following a CAT III arrival, the rule is to keep the trailing aircraft off the runway until the CAT III has landed and cleared the runway. That’s why the required separation is described as being clear of the runway.

This isn’t about a fixed distance on final; it’s about ensuring no risk of conflict with the CAT III’s landing and rollout. Being on the runway or on its threshold while the CAT III is landing would create a potential collision or runway incursion, so the trailing CAT I must be kept clear of the runway until it’s safe to proceed.

In short, the trailing aircraft must be clear of the runway to preserve safe sequencing and provide adequate space for the CAT III arrival to land and vacate.