Saw about a dozen balls of fire in the sky, some traveling together, moving north to south in a time frame of about 15-20 minutes. Night time, but no tails visible, moved slowly, taking 2-3 minutes to travel from horizon to horizon. The light flickered slightly to appear more like a flare, rather than a light. There was no sound and no way of telling altitude. At first we thought they could be flares attached to skydivers, but unlikely considering they traveled more laterally than would be expected for a skydiver. Eventually, it appeared some fizzled out as they began to approach the departing horizon to leave our line of sight. Too slow to be a flare shot across the sky, but wasn't sold on it being debris entering the atmosphere either.