The F-4 sparowhawk was the replacement for thhe previos F-1 in the fighter role and realy what the Northern Lights Air Force wanted in the first place it had the VD-41XL engine in the production variant the prototype caried the Avaion AG-400D engine but that was 1. Too complex to build in mass numbers and 2. It was an osiris engine and getting a permit to build an engine for a plane that was going to be used against a nation wasnt realy a plausable solution so the VD was added to the end of the designation the plane would come into service with the (NLAF) right before the 2nd unification war and would replace the F-1 by the middle of the conflict the navy at first didnt want it although they were foced to use it on the grounds of its the only thing they had the navy would later get its own fighter the F-4 served thoughout the 2nd unification war and the 3rd unification war however it was replaced by the F-75 during the 3rd unification war and would stop production of the F-4 after the war in total 2534 F-4s were built that inclueds all moddels