Last month our Ding! special $59 MDW-LAS flight was delayed in arriving at MDW from somewhere else by a bit more than 1 hour due to a mechanical. We learned about it before an earlier flight left. They gave us Rule 85 no-charge standbys on that earlier flight and we got on. The GA at our original flight said that typical practice was to allow no-charge earlier flight standbys if your flight was delayed >= 1 hour coming in, but of course that may just be MDW practice. We were easy to accomodate because we had no checked bags.