40-50,000 ft heading 255-265 degrees for 4 minutes then sharp left turn to about 160 degrees

Saw large rectangle object leaving large con trail faster than airlines up about 40,000-50,000 ft heading 255-265 degrees and north of Madison Alabama. Watched it for about 4 minutes, then made sharp turn to about 160 degrees, accelerated and was out of sight in about a minute. Clear skies and no wind at that altitude since the con trail was not drifting to the side. There was no sound and no lights. It was very shiny.
I am an Aerospace and Mechanical Engineer, pilot, test pilot and bush pilot. 40 plus years developing state of the art aircraft, engines and propellers. My work has been tested by NASA senior engineers and FAA engineers