It was just before storm. I was walking out with my dog.From south-east came large clouds, it was also very loud (thunders out of stormy clouds on east). I was just going back to my blockhouse I live. From south-east I saw a black point flying fast just under clouds high above neighbour hous roof. First I though ahat I see large bird flying with big open wings. But speed of this flight was incrridable...I was trying to see if there is any kind of vertical like motion ( of wings) or any monouvers done by object, but not... It was going like on wire-straight ahad like sattelites in night sky. But it was light and storm was just coming.Object was dark(black), rather rectangular like. I was observig flight from south-east to north-west(west) direction. It took over 3-4 min of observation. In my opinion it wasn't a bird, perhaps aircraft, but it was no sound like and no stripe, any steam, any trail anythink what should be sign that it is an aircraft.... Supersonic Big bird???