Stream of perfectly spaced light objects

We just witnessed a string of perfectly spaced lights traveling together for at least a few minutes.  Long enough for us to stare and repeatedly ask ourselves what we were seeing.  Estimated total was between 30 to 50 objects.  At first I thought they were coming from the ground and exiting the atmosphere but I now believe what we were seeing was them crossing or skimming the upper atmosphere.  They seemed to appear from no where on the horizon, would then get very bright as they entered the middle of the stream, and then fade out.  All while maintaining perfect spacing and formation.  The stream of bright objects flowed for an estimated two to three minutes nonstop.