[AI] Nav mesh only created around editor-time created characters?

The following is a picture of my level with a single enemy and 3 cubes. The ground is a plane.
The selected volume is the nav mesh bounding volume.

As you can see the nav mesh is only created around the enemy. if I move him more areas are created.
However if I just run the game - only the area you can see in the picture is created, and the enemy won’t follow behind it.

What am I missing? how can I build nav mesh for the entire plane?