Complex sentence: The F-94C Starfire was significantly modified from the early F-94 variants; in fact, it was initially designated F-97, but it was ultimately decided to treat it as a new version of F-94.
Split into simpler sentences: The F-94C Starfire was extensively modified from the early F-94 variants. In fact, it was initially designated F-97, but it was ultimately decided to treat it as a new version of the F-94.