Metallic/Gray orb was flight just above a layer of clouds in the opposite direction of my flight.

I was on an Alaska Airlines flight from Miami to Seattle this past Sunday, June 4. The flight was scheduled to land at 9:25 but we landed a little early.
I usually sit in seat "A" (left side of the plane) so I can take pictures of the mountains (Rainier etc.) to the south before landing in Seattle.
I am not sure whether I was in Eastern Oregon or Washington but I started looking out the window for mountains in the distance. We were flying just above a layer of clouds and there were several breaks in the clouds.
There was a layer of clouds below us and that's when I saw this gray circular-looking orb just above a lower layer of clouds traveling eastward (Opposite direction of Seattle). I've seen planes go the other way before and they never appear to fly in a straight line.
This thing flew in a straight line and was going at least as fast as a commercial airplane. I followed it with my eyes until I couldn't see it anymore. I was close to the front of the plane in 6A. Once out of view, I looked back in the plane but I didn't hear anyone react. Maybe no one else saw it?