The mix of military aircraft at Marine Corps Base Hawaii at Kane'ohe Bay would change substantially beginning by 2012 under a plan released yesterday by the Navy. All but three of the Navy's 27 aging propeller-driven P-3C Orion surveillance and reconnaissance aircraft would be replaced by 18 P-8A Poseidon multi-mission jet aircraft based on the Boeing 737-800, but with strengthened wings, weapons systems and added fuel tanks.