Complex sentence: Although, Pakistani pilots flew J-5 in air combat missions for Syria during some of the Arab-Israeli conflicts; according to Israeli pilots, the Pakistani pilots that flew and fought for Syria were more formidable opponents than Syrian pilots.
Split into simpler sentences: Although, Pakistani pilots flew and fought J-5s in air combat missions for Syria during some of the Arab-Israeli conflicts. According to Israeli pilots, these Pakistani pilots were more formidable opponents than Syrian pilots.