Why two carriers cannot guarantee a carrier group

Are Britain's aircraft carriers underperforming, and what would guarantee carrier availability?

The ships are not the core problem; a guaranteed group would require four carriers and proportionate destroyer, frigate, support-ship, and submarine forces.

Two carriers can provide capability when maintenance and mishaps cooperate. They cannot guarantee that a carrier group will always be available. The four-boat strategic-deterrent model distinguishes intermittent, routine, and assured readiness. A notional guaranteed force includes four carriers, twelve destroyers, sixteen frigates, four support groups, and four SSNs. A flight deck's availability depends on the escort and support fleet around it as well as the number of carriers.