CT-57/11-9048 was a clone trooper pilot who served in the Galactic Republic's 127th Gunship Wing during the Clone Wars. In 19 BBY, he fought on the planet Cato Neimoidia, flying an ARC-170 starfighter. When Order 66 was issued by Supreme Chancellor Palpatine, CT-57/11-9048 and Captain CT-55/11-9009 killed their commanding officer, Jedi Master Plo Koon, while they were escorting him on a patrol of the planet's bridge cities.