Saw craft hovering outside of window while in flight

Was looking out the right side of the plane window when an object that looked like a drone appeared to come from beneath the aircraft hovered at the window and then took off away from the plane. It had 1 red light on it!  It only had red lights on it myself and three other people saw this and another person asked if anybody else has seen the UFO. I said I saw something that looked like a drone and the partner in the next seat said we’re up 20,000 feet it can’t be a drone. I asked the captain when we got off the plane if he saw it he just laughed and said no I didn’t see anything.