I am sure of "lines" and a runway ON TOP of chopped off mountains.
I have seen it somewhere a long time ago.
Sounds like a Von Daineken(sp?) type explanation.
Did you hear about these mountains?
Was this on a tv show?
Maybe the discovery channel or national geographic?
Was this something you read in a book?
What you describe in the initial post sounds like part of a movie about a plane crash. It was an actual account of a true story. The plane crashed into a mountain "chopping off" part of the mountain top.