Realistic horizon

I was thinking about making a combat flight simulator in unity. I know that when you get up high in a plane, the horizon gets really bright and hazy off in the distance, like this picture: http://www.jaxhouse.com/wp-content/uploads/2012/04/planeCHicagolanding.jpg. Does anyone know how to do this or anything close to it?

http://docs.unity3d.com/Manual/class-RenderSettings.html is a good start