Unidentified S shaped flying object spinning across sky

We noticed a strange metallic object reflecting light in the sky and spinning around and drifting. It looked to be the same distance away as the jet planes we also saw flying that day, but further away than the planes taking off from the nearby SeaTac Airport. Based on this distance it was around the same size as a small jet plane. It was S shaped (letter Z, number 2 or 5, etc). It spun around but did not follow the same direction of the wind that the clouds were being blown in. It changed direction, descended a little bit once, changed direction again, and then ascended out of view. It is unclear if the lights that we were seeing were from the aircraft or if it was reflecting sunlight, but it did seem to be propelled by its own power source.