I was standing on my balcony, smoking a cigarette and watching a bat flying around some metres away. in the background i did notice another dark flying thing. at first i thought it was a bird, seconds later when it came closer i thought it was a plane. the object at first seemed simply dark (maybe black or grey, which is hard to tell in the evening sky) and had a round shape, which i could observe when it was at the closest distance to me on its flight. it did not emit or reflect any light and did not make any sounds. when i thought that this wasn't a bird or a plane (no wings on it, round shape), i walked down on the balcony, so that i could observe it further. the object flew a straight route, roughly the flight route from bremen to hamburg but much faster than airplanes. it didn't make any turns or changed its speed, finally vanishing in a group of clouds. i also realized that the bat had been gone and didn't return until the object had passed some seconds before.