Flying saucer spotted over Boulder City in 1951

On April 18, 1951, two friends were driving on a road in Boulder City (Colorado, USA). Suddenly, they have seen a huge flying saucer in the sky.

Witness report:

I, age 21. Was at my house one April night when a friend stopped by and asked me if I wanted to go for a drive. I said yes, and we drove out around a power plant outside Boulder, Colorado. The power plant was called Rocky Flats, and on the opposite side of the road, there was a field. When we drove by the field, all of the sudden there were these rotating lights in the field by the side of the road. I immediately thought that it was a flying saucer. The driver stopped and parked, and we just sat there in silence watching this craft. It had a silver exterior and all the lights that were rotating around it were all white. They didn't blink or anything they just rotated. I felt like I should leave the car and walk up and touch it, but I knew my friend didn't want to so I just stayed in the car. After about 20 minutes of just sitting there watching it, it just zoomed straight up in the air and flew away vertically out of sight. We didn't get out of the car and check the field or anything and we didn't see any little green men, we just drove away and didn't say anything to each other for a long time.