Large oval object with white glowing lights moves slowly above the car

My husband and I were returning home between 22:00 and 23:00 on a cold but clear night. On Colorado Highway 7 about 2 miles north of Lyons, Colorado, I caught sight of the underside of a very large object.  It seemed to be oval-shaped, maybe 50-75' long and 25-35' wide; there were glowing circular white lights on the bottom of the object. The lights were bright enough to help me make out the edges of the object.  I could see 4-5 of these lights, which seemed to be placed toward the outer edge of the object.  It was moving very slowly across the canyon, about 20-25 feet above the car.
I asked my husband if he was seeing the object.  He did not respond but kept driving, staring intently ahead, and giving no sign that he had heard me.  He did not remember anything about this when I questioned him the next morning.
I am presently a psychoanalyst in private practice.  Before I changed careers, I was chief of a large fire protection district in the western U.S.  Before that I was a naturalist with the National Park Service, and have long been a student and observer of nature.  I consider myself to be a curious, careful and scientifically oriented observer.