two similar quasi-invisible airborne circles

by themselves, neither one of these reports is all that interesting, but I find it curious that within a couple of days of each other, there are these two reports that are so similar as to be very eerie. Both are very subtle circles hanging motionless in the sky, hardly visible....
The first is the one from Kings Dominion, VA, which actually has some video to go with it.
The second, is a single photo that only showed a strange circle when the photographer was looking over his photos after uploading.
By themselves, either of these could be easily dismissed as whatever, but these are 3 days apart, this particular one from Texas. I just found that curious enough to post both of these as a potentially related phenomenon.
Also if you poke around the YouTube video some, you'll find this one, which shows some other similar rings from previous decades, with some more discussion on the 1957 sighting available at UFOCasebook.