There are five imaginary surfaces that make up an airport's navigable airspace. Most aviation accidents happen in the primary surface, and they are usually the flavor of runway incursions. Do some research and tell the class why you think these runway incursions happen. Then take a moment to discuss some of the technical and the non-technical initiatives that are intended to make airport surface operations safer. Are there any particular initiatives you would advocate? Why? Your initial post should be at least 250 words.