White spot in sky from east to west stalled when nearing a commercial airline then rapidly disappeared

Brother and I spotted a white circle in the mid day crossing the sky from the east at high altitude. Watched in amazement and confusion for twenty seconds or so cross the entire horizon directly over us. At one point appeared to near a commercial airline where it slowed then continued flying out of site. Moved too fast for anything I can associate with. Object was bright white perfectly round appeared to have slight distortion in shape of triangle like a cylindrical tail so to speak. No visible trail or evidence was left behind. Unfortunately we were so mesmerized by the object we did not get any pictures.