At sunset hovering slowly just below the clouds

It was slowly hovering above Queen Valley AZ, just below the clouds which were more solid and shaped like a submarine stretching to the west. It was motionless when i first saw it then it slowly moved Westward, Altitude approximately, 3-4k ft up, No shape of wings of aircraft or bird. Just oval/oblong dark. It began moving slowly towards Phoenix to the west, It did pick up speed but not too fast. Faster than a single engine airplane can go but slower than a jet. It kept close to the bottom of the cloud for cover. It finally disappeared into the cloud bank far to the west. I did not take a video as I was too stunned to believe it myself. Most importantly, it was dead calm silent at that time and I could hear nothing.