Radar-directed CAP replaces simple launch warning

When Illustrious operated Fulmars rather than the expected interceptors, the Royal Navy returned to combat-air-patrol methods tested in pre-war exercises. Radar allowed controllers to direct aircraft already in the air instead of merely signalling a deck launch. HMS Eagle's Sea Gladiator operation still followed an interceptor policy, even though Eagle is sometimes cited as the starting point. Illustrious pushed the patrol outward and made airborne direction central to the fleet-defence problem.