One route changes the losses of Courageous and Glorious so the older strike carriers survive for Mediterranean service. Courageous might take damaging rather than fatal torpedo hits, while Glorious could remain with the fleet or maintain an airborne patrol before encountering Scharnhorst. The other route completes Formidable roughly two months early and sends her east with Ark Royal, temporarily stripping the western basin of carrier cover. Hybrid combinations could preserve one older ship and add either Ark Royal or Formidable as the fourth deck. The older carriers' survival is the easier divergence because comparatively small changes to their historical losses can keep them available.
Chapter · 55:39-1:00:10
Two plausible routes to a four-carrier force
The counterfactual can preserve Courageous and Glorious or accelerate Formidable and redeploy Ark Royal to join Eagle and Illustrious.