Well, might we have a solution for the Heflin photo case? According to an anonymous post to UFO Updates, the object is in fact a model train wheel, and the smoke ring in the final Heflin image is from an airshow. Let’s take a look, shall we?
First, here’s a comparison of model train wheels with two of the Heflin photos… and then a comparison of the final Heflin image and an airshow photo (including the aircraft which created the ring).
Not conclusive, but mighty compelling justification for a re-evaluation, wouldn’t you say?