Large floating UFO near Portland, Oregon airport as seen from planeAt approximately 19:30, I was on a flight as it approached Portland International Airport. I was seated in a window seat approx. 6 rows in front of the wing at that time. Around 15 minutes prior to landing (NE approach), I noticed an unidentified object in the sky, while viewing the landscape below. We were still several thousand feet off the ground (houses were approx. 5mm in size) at this time. The object appeared to be stationary and approximately 1000 feet below us and to the left of the plane. It consisted of a cluster of round metallic objects making up the top half of the craft, which via a circular midsection joined an elongated four sided pyramid as the bottom half. All areas of the craft were silver and reflective in nature. The top half can best be described as if you created a larger sphere out of adjoining smaller spheres. This top half was not elongated or billowing in the wind as a weather ballon might do.I observed the object for approx. 5 seconds, as my plane passed by. My view of the object was excellent. There were no clouds in the sky, and I could see multiple details of the craft. I did not note any vapors or heat waves emanating from the craft. After we left the craft behind, I began scanning objects on the ground to reference the crafts size. My best guess is comparing it to a semi truck while we were 600 ft above it.Others may have seen this craft but no one said anything on the flight. Unfortunately we passed by too quick to take a picture, but I am 100% certain of what I saw.