In addition to the RB-66B, RB-66C models entered service with the 9th Squadron in February 1956. RB-66C models carried additional electronic countermeasures (ECM) equipment in wingtip pods. Chaff dispensing pods could be carried underneath the wing outboard of the engine nacelles. Later examples had the tail turret removed and replaced by additional ECM equipment installed in an extended tailcone. After the tail guns were removed, the gunner's position was usually left empty unless occupied by an instructor pilot or instructor navigator.