*please check the achievement "Maxed" too, as there are handy tips for gaining XP there aswell*
i thought i would say another good map apart from the one written by x g xxx under the "Maxed" achievement for this game for XP is the level "malestrom"
its over sea and there are waves of frigates and different ships to destroy each with at least 50XP per kill. not to mention the many SU-47 berkut's that fly around which (im pretty positive) has the most XP for shooting down an enemy aircraft (35xp).
also a good tip is to crash when you run out of ammo or just after a finishing off a wave of naval ships. you get to keep you points AND refill ammo AND re-kill the last wave of boats for like 50xp a kill. also at the end of the level there are around 6ish bombers to destroy all flying slow and un-escorted so easy kills ahoy! so as you can probably begin to tell, your points will soon stack up
play on recruit too, because on harder settings you get less ammo and health! ;)
depending on how many times you crash on purpose to re-kill enemies and refill ammo you should be about the 4000xp mark per game.
i would say there is 75% naval and 25% air enemies in this level so i would advise AGM missiles (only 2 hits to sink a boat) for the boats. heat seeking wont lock on to ships but joint strike do, but your looking at 3 to 4 joint strike's per boat which isnt too good so stick with AGM's i'd say :)
for aircraft, its up to you. heat seeking / multiple missiles / joint stike are all pretty good a downing enemy planes as you probably know, so go with what you feel comfy with.
if your averaging 4k xp per level, it wont take much time to level up pretty fast aswell, also adding towards the "Maxed" cheev. so your kinda getting 2 for 1 on achievements if you know what i mean :)
OR you can always boost which is a bit faster. but very boring!
hope this soloution helps. even if its just a little! ( :