Could you land a large airplane on short circular runways?
As a matter of physics, there's a certain amount of braking and steering force available to the aircraft after it lands.

Suppose the aircraft touches down moving due north, and continues clockwise around your circular runway. After a quarter-circle it travels due east -- but that means that enough braking force has been applied to reduce the northward component of its velocity to zero, while also giving it some eastward velocity.

If only that eastward force hadn't been applied, the aircraft would be at a halt now -- using less force than what's necessary for it to follow the circle.

So if the plane can keep itself on a circular runway, it will be even easier for it to come to a halt on a straight runway whose length is the radius of the circle.



(Also, the plan ignores that the critical factor in the length of runways is not landing but taking off -- there must be enough runway to brake down safely if the takeoff is aborted just before rotation. And taking off from a curved runway sounds even crazier than landing. If the runway is horizontal, the plane would become airborne in the middle of an uncoordinated turn...)