If a pilot were to call mayday and say they're landing on runway 6 everyone would be trying to ensure runway 6 was clear. The only way 6 would be blocked is if there was something already on it that couldn't be moved in time. Think of a mayday call as the lights and sirens of the sky.
Yeah--the point is that a plane under robot control like that is going to be calling mayday and everyone on the frequency is going to make way for it if possible. You make way for a plane calling mayday like you make way for any vehicle running lights and sirens--but in the sky there's a lot more ability to make room and a lot more enforcement against anyone who doesn't obey.
