Over several years (I first saw it in August 2001) I've seen objects in the sky that first appeared as stars (no movment visible) until these objects started to move until with direction changes until the went over the horizon. Within a second these objects accelerated to a speed that was way faster than the ISS passing by. I've seen the MIR, the ISS and several salelites and I've never seen any of them standing still and then accelerating this fast, even making changes in direction.