While under repair in 1941, "Illustrious"s rear "round-down" was flattened to increase the usable length of the flight deck to . This increased her aircraft complement to 47 aircraft by use of a permanent deck park of 6 aircraft. Her light AA armament was also augmented by the addition of 10 Oerlikon 20 mm autocannon in single mounts. In addition the two steel fire curtains in the hangar were replaced by asbestos ones. After her return to the UK later that year, her Type 79Z radar was replaced by a Type 281 system and a Type 285 gunnery radar was mounted on one of the main fire-control directors. The additional crewmen, maintenance personnel and facilities needed to support these aircraft, weapons and sensors increased her complement to 1,326.