Looking out window saw large vertical rectangle. Stationary. Plane moving, object was in stationary position.

Personal Note:
Friday, May 6
On flight to IAH from LAX
Had my head against window. Was just woken up by man behind me talking. I looked out the window as it was leaving my vision.
Man seated behind me and I both saw something very odd outside, by the plane windows.
Shaped like a white fridge or milk carton. Flying upright. Taller than shorter.
Did not fill my view but perhaps from size of building to size of taller refrigerator, depending on distance. Very clear and crisp.
Plane moved object was stationary
While departing, the Gentleman behind me thought it was black, (when I asked him) I thought it was light, not shiny though.
As we passed it I thought it was the color, but not shape, of a cloud. It had edges like a box, perhaps it had more sides unseen? Therefore maybe not a rectangle? No openings such as door, windows, vents, seams, etc. it was seamless.
At the time, I didn’t think much of the event. I felt like it was the most ordinary thing in the world. Like traveling in a car on an empty road and seeing a huge box by the road.
No signs of life outside the window, or around the object.
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