What is this aircraft seen at Peachtree City, GA?
It's one of many privately owned Aero L-39s, some of which are in the US. Here's one registered in Georgia, USA, with a similar livery at the same airport:


(flickr.com) N915WE.


  N915WE Aero L39C
  Preparing for takeoff. Falcon Field-Peachtree City, Ga.


It could actually be the same one you photographed.