An unusual flashing light

At 8:43-8:846 last night my Husband and oldest son were sitting on the back porch when a lower (lower than airplanes) flashing light was seen to the west. It was dark and cloudy out and moving extremely slow in the sky. For 3 mins we watched this bright slow flashing but continuous light was creeping through the sky. There was only one light. It slowly, very slowly faded away. We've never seen anything like it in our sky here at home. It was very bright in the clouds and several miles away you could tell. Planes and aircraft fly through these clouds and areas all throughout the day and we've never seen a light like this one.