Plain English Meaning

Someone or something is on a runway when they shouldn't be. That could be another aircraft, a ground vehicle, a person on foot, or even an object — and their presence puts them in the way of aircraft taking off or landing.

Full Definition

Any unauthorized presence of an aircraft, vehicle, person, or object on the protected surface of a runway designated for the takeoff or landing of aircraft. A runway incursion creates a collision hazard or otherwise reduces the required separation between an aircraft and another aircraft, vehicle, or person on or near the runway.

Context Anchor

You will see this term in airport diagram use, taxi planning, ground control instructions, and safety discussions about moving around an airport.