I saw a bright white liht in the sky at 05:00am,It was at niht,the sky was clear of clouds.The altitude of the liht was between 2 to 5 kilometers,the speed was slower then a airline plane.It glowed every 5 seconds on and every 5 seconds of,it continued with that secuense loosing and gaining liht also taking 5 seconds to gain or to loose intensety of liht.It flew initialy north to south(over the airport of faro)as it reacht the sea it turned to east slowly and after a while back to north until it disapeard,the glowing liht never changed speed or altitude,and never made sound. I work on the airport of faro,my job is to give ground asistence near the planes. I am shore that what I saw was not a plane. . .