"Dead space" in a diorama.

Might you be able to post a picture? A visual might stimulate the imagination...

Steve 

Well, since it's a runway, you can't really load it up with vegetation; trees, bushes, etc.

Or livestock?...hmmmm...

That's a tough one....I agree that a photo might help us help you.

Then again, if your action is located in a focal point, you may not need much at all in that area. Sometimes dead space is ok, if it doesn't distract from the focal point. Even something simple like some flowers or some color variation can just provide some surface variation, and that can be enough.

Here's what I would do--skew the plane at a 45* angle--don't put it absolutely parallel to the base's sides. That way, you have a larger space in front of the plane, and your focal point is more powerful. This is one of the "rules" of diorama's anyway--never put your central elements at parallel angles to the base's sides. This arrangement would really solve your problem. Your focal point would be front center, and the dead space in the rear would not even be noticeable.

Perhaps a Squad of Soldiers at "Inspection Arms" attention.  Changing of the airfield guard or something of that sort.

rb

  You could put some crates there stacked in a couple of rows with one or two guys with clipboards checking them off before being loaded.