I once saw something I can't explain. Two spots on the night sky a bit larger than a star and of the color of an incandescent light about a half thumb on an out

I once saw something I can't explain. Two spots on the night sky a bit larger than a star and of the color of an incandescent light about a half thumb on an outstreched arm apart. They were slowly moving across the sky, however with a swinging movement forward and backwards about a thumb with a period of two seconds. Like two people side by side walking together two steps ahead then a step back the whole time, just in the sky and this was a smooth movement. Then suddenly one of the two lights went out. The other one continued the same movement and also went out about a minute later. This steady swinging movement is an unexplainable riddle for me. A friend of mine also sighted something in the bright day sky of Spain. He told me that he looked up and then that thing whooshed away in an incredible speed over the Mediterranean Sea. It's really weird. Either our senses and even the technical equipment like cameras are just fooled or we have extremely strange things going on over our heads.