Cheats
Once you have started up the game and reached the main menu, you may type "snap" to unlock all of the planes in the game for use in instant action or campaign missions. If entered correctly, a Marine in dress uniform will tell you that "You are a cheater." Alternatively, if you are only interested in unlocking the Japanese planes, type "japs" instead. You will receive the same confirmation message.
These cheats will need to be entered every time you start the game, and the unlocked planes come absent of any upgrades. Also, the game's autosave function will be disabled while either of these cheats is active.
Historical Missions
Apart from more aircraft, Heroes of the Pacific also has five unlockable missions that are based on historical events. Unlocking historical missions requires that you beat a corresponding campaign mission. For instance, to unlock the historical mission "Against all odds," you must first beat the campaign mission "Evacuate the Admiral." Other campaign missions that unlock historical missions include "Battle of Midway," "Backs Against the Wall," "Million Men" and "Revenge."