I always wondered, when the invasion finally started in the movie Signs, and the swarm of aliens started closing in on the Hesses and their boarded up (from the inside) house, where were their UFOs? Were they parked in the crop circles or parked in the backyards or somewhere else?
We don't know
In fact, as I recall, the we only see the spacships as lights in the sky in a news report.
Their physical location once landed (assuming they do) is not stated. It might be that these aliens we see on the ground are a "landing party" and the spaceships are, in fact, still in orbit.