My mother says she went out to put the horse in, and she saw a flash, looked up and saw 4 groups of lights flying in formation fly over and disappear behind the trees.

I know this story is a little old, now, and sorry we cant remember the exact date. My mother came in late one evening about 11:30 and told me she saw a UFO. She went out to put the horse in the barn, and she saw a bright flash from behind the trees to the east, which made her think of shooting stars. So she looked up to see if she could see any more. She noticed something moving in the big dipper, and initially thought it was a meteor, or satellite, until she realized there were 4 groups of either 2 or 4 starlike lights, in a rhombus formation, with 1 group in front, 2 on each side, and one trailing.    
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Each one 'waggled' or yawed a bit in mid-flight, and then carried on until she lost sight of them behind the trees to the east, roughly where she saw the flash (the flash was like a flare that descended and dimmed, but she could not see the source for the trees). There was no noise. It was travelling at a pretty good clip, faster than a typical airplne, slower than a meteor. If it was a plane/jet, there would have been sound and colored/ blinking lights. Left no trail. Very clear sky. The whole thing she estimated to be the size of a dime at arm's lenght, or smaller. Each group of lights was as bright as a moderately dim star, no brighter than one of the big dipper stars. Whole time from flash until the craft disappeared behind trees was probably 15 to 20 secs max. The fir trees to the east are tall, and obscure the sky up to about 45 deg. I have noticed similarities in this story to the one from the man in Knoxville, TN, also in your database. I hope the diagram I drew above will work. (It likely will only work in the font used to enter it into the database.)