Wirelessly posted (BlackBerry8830/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/105)
I am not aware of an OK ATL-PRG flight. I think you might be seeing a DL codeshare. That would be a DL 767 which would be better than the typical OK TATL service, which is similar to domestic F and not recommended.
CO doesn't serve PRG, so anything with a CO code is a codeshare flight. Look at the operating carrier to make that decision.