What is the correct action when you observe a runway boundary crossing without clearance?

• A. Issue an immediate stop instruction and clear the traffic path; inform ground
• B. Ignore and let the aircraft cross
• C. Ask the pilot to circle once
• D. Notify the control tower after the fact

Answer: (A)

When a runway boundary is crossed without clearance, the immediate priority is to prevent a runway incursion and protect everyone on the surface. The proper action is to issue an immediate stop instruction to the aircraft and, if needed, guide it to clear the remaining traffic path. At the same time, inform ground control so they can coordinate and ensure other vehicles or aircraft are stopped or redirected as necessary. This rapid, decisive instruction stops the unsafe movement right away and creates a safe, controlled environment for resolving the situation.

Delaying action or asking the pilot to circle does not address the immediate risk to other aircraft and ground personnel, and notifying the tower after the fact is too late to prevent a potential accident.