Flashing white light following civilian plane at high altitudes. The extremely bright white flashing light was traveling west, stopped and changed course to follow civilian plane moving south. Planes do not fly in such a manner and there were no colored lights as required by US law. But the idea of a bright flashing white light stopping on a dime, changing course and speed to fall behind a civilian plane and then trail said aircraft from a distance. Believe it or not, tower does not allow 2 aircraft to be that close together. Nor are planes allowed to fly in US airspace without green and red lights with a white strobe.