Round craft with bright emerald lights flashed and disappeared the second time the lights flashed.I was looking up to the east and saw an aircraft flying from the south, going northeast at about 3500-4000 feet. This craft was not completely circular, and was not quite oval. It reminded me of the shape of a crown. I could see the bottom and sides of it. It was moving slightly faster than the planes that come from the north towards Williams airport. It had only once color of lights. It had two horizontal rows of bright green lights around it, and around the craft, there were some vertical bright green lights in sections. The top and bottoms of the vertical lights seemed to extend from the craft. As it moved, I saw a sudden flash of the lights getting brighter, then back to the original green. It continued moving, and when in mid sky, in reference to my vantage point, the lights flashed brighter a second time. After they flashed, I saw only sky and stars in its place. There was no sign of the aircraft. Also, there was a rough, low sound during the time I sa! w the air craft, but myself and the other person who wasn’t looking at the craft thought it was a car or some machine in the neighborhood, although an odd sound. When the aircraft disappeared, the sound stopped. I've seen strange lights over years, rarely, but this was an actual aircraft unlike any that I've ever seen. When the lights flashed on and then it was gone, it took me a moment to realize it was gone and not falling from the sky, which is what I would have expected.