Nobody schedules an empty leg. One shows up here because an
operator has an aircraft finishing a trip near Janesville and needs it near
the San Francisco Bay Area, or needs it home and this direction happens to be the way home.
That is why the flight can be a fraction of a full charter, why it can
vanish within hours, and why the return direction is a different flight
entirely with its own price and its own aircraft. Watching the route beats
searching it once.