It about five after ten on a clear wind calm night. A friend and I were in a natural area on the property of a local hospital listening for owls. Suddenly a craft flew almost straight over head going towards the hospital. Thirty seconds later an identical craft flew over in the same flight path. The only reason we saw them was because the hospital parking lot lights lit up the under side of the crafts. The parking lot was on the other side of a tree line. We were on the other side of the tree line in an open prairie. The crafts were triangular in shape and were wider than long. I`d estimate they were 15 feet wide by 10 feet long. They were a light grayish brown with a very dark strip that bordered close to the entire back end. They were traveling 10 mph and were around 80 feet off the ground. The crafts flew in a straght line and made no noise. They had no lights that we could see.