A string of rectangle e=devices in a straight line moving across the sky

Last evening, September 19th, three of us were standing in the street, Cyprus Drive in McCormick SC walking our dogs. I looked up and saw a train like procession of rectangles crossing the sky. They looked like dominos, each with two or three horizontal lights, traveling in a straight line. There was no engine sound and they were moving at a rather fast pace although it is difficult to judge the speed. None of us had ever seen anything like this.