I am an airline pilot. I have flown in the Pacific for 23 years. I have never seen before what I saw on the 4th of October, 2014. The moon was not up. The sun was 2 hours from coming up. It was a very dark night. We were flying about 1500 miles west of California at the time. I was looking out the windshield and saw a perfectly round, white, cloud-like form. It appeared to be 80% above the horizon. It looked like a moon rising above the horizon but 4 times as big. The outer edge was brighter than the center. Our flight path was taking us through the left edge of the form. The form was a perfect circle. I couldn’t tell at first if it was a flat circle or a sphere. As we got closer, it got larger. We were at 39,000 ft. The upper edge of the circle was many thousands of feet higher than we were. I would guess 100,000 ft. or higher. We did fly through the left edge of this. As we got closer it diffused and was harder to see. There were 2 other aircraft that saw the same object that night. One of the aircrafts was 40 min. ahead of us that saw it. Because it was so dark I am not sure why we could see this. Normally on moonless nights, clouds and such are not visible. I do know it wasn’t the northern lights and it wasn’t some strange cloud.