The single-seat fighter Illustrious was meant to carry

The intended air group included a compact single-seat fighter derived from Supermarine work related to the Spitfire. Without that aircraft, the Fleet Air Arm used the larger two-seat Fulmar for fighter and reconnaissance duties. With the smaller fighter, the estimated complement rises to eighteen fighters alongside twenty-four torpedo-spotter-reconnaissance aircraft. The Supermarine proposal is an example whose surviving sketches, timing, and specifications appear to fit the carrier programme; other aircraft companies also seem to have been involved. Its proposed gull wings offered strength and extra clearance for carrier landings. The air-group estimate therefore depends on an aircraft that was never available for Illustrious's wartime service.