I had such a blurred memory from the times I was about 4 years old. I was playing on the playground with another kids and when I was swinging on a swing I looked at the sky. There were some clouds but between them i could see the pure blue sky. I liked to watch the sky a lot so I was enjoying the fun on the swing and looking at the sky at the same moment. For a few seconds I noticed 3 objects that were flying between one cloud to another, for about a 10 seconds. I had that feeling that them couldnt be birds because they looked completely different, each of them had similar to circle, but a little bit slightly different shape.
But again as I said. I can't remember if it happened for real or if it was a dream. I'm pretty sure that the first option is true but not for 100%.