I thought it was Starlink at first but I zoomed in and noticed there was a dome in the center of the disc. Plus the light shape didn't match Starlink. I contacted the local air traffic control captain but he said nothing showed on the radar at the time of my report. The disc moved smoothly in one direction then all of a sudden changed. Then it gradually just faded into the dark (not the distance), just faded into the air. Not a sound was heard. and based on the distance away and a the size, I'm guess it was several hundred feet wide, at least.