Fights are absolutely essentially basically everywhere besides Europe and North America - especially South America, Africa and Asia. The most important area where fighter cover will be necessary is probably in the Mediterranean, especially in multiplayer or against DAIM. Why?
Because the allies will have strongholds in north africa, but will need to invade Greece/Yugoslavia/Italy - interceptors wont make it across the ocean while fighters will. Escort fighters are not enough to hold off enemy air superiority, nor run large patrols to protect your fleets (because if your on time... your light carriers, if any, wont be advanced enough to fend off naval strikes). While the vanilla AI is pretty poor at using air superiority and using naval/tactical bombers to halt attacks, a properly functioning air force, through multiplayer or through an AI mod, will make it impossible to invade mainland italy without fighters.