Hovering UFO

The object appeared as we were still in a High School football stadium outside during a graduation ceremony. We (many around the seats were sitting on) noticed a disc shaped object hovering over the Santa Catalina Mountains above the city of Tucson to the east of our location and north of Tucson.. At the beginning of the sighting, it was a hovering without any lights. Many of us speculated that it was an airplane - only it was not moving. The object simply hovered for about 10 minutes high in the sky. We attempted to take a phone but out camera photo was not capable of Suddenly the object begins flashing a single white light then it appeared to have more than one light flashing. Some people thought it was a plane from the nearby Air Force Base (Davis Monthan) but it was not moving - just hovering. Some thought it was a helicopter but again it was not moving. Suddenly it moved very rapidly from the east of us to the south of us. I would estimate it moved about 20 miles directly over Tucson. No airplane - military or civilian- could possible travel this distance in about 3 seconds. The object hovered over Tucson for only a few minutes then flew directly downward, almost appearing to be in a free fall. It disappeared after that.