Select geometries below a plane

Hi, I was looking for a way to select the geometries that are below a plane. for example:
I have a set of lines, and a plane in x,y,z cordinates, and I’d like to select the lines that are below. Like I show in the picture.

Extract endpoints from the lines and check their z value, compare this with the z of the plane and make a cull pattern based on it. If you need more help post file.