Hobbies And Interests
SR-71 Blackbird Weapon Pack
Also known as "The Big One" weapon pack, the ACE bonus objective must be completed in the final mission (mission 4.5) and the SR-71 weapon pack must be added immediately upon completion. This will give you an A-SLAMR, which is a super-weapon--a nuclear missile that destroys everything. This weapon does not recharge once it is fired, so use it wisely. With this weapon pack, you are almost unbeatable.
Standard Weapon Packs
Flying a variety of missions under a variety of difficulties in combination will ultimately unlock all of the weapon packs. Flying all of the Mission One levels under Ace difficulty will unlock half the weapons packs for planes in the game. Oddly, flying the second mission levels under the rookie difficulty will unlock the rest of the weapon packs in the game, except for the aforementioned SR-71 special weapons pack. These weapons packs mean very little if you don't have the corresponding aircraft to actually use these weapons packs on.
Aircraft Unlocks
Attaining aircraft for Heatseeker is the other half of the cheat puzzle, so that you can actually use the weapons packs you have acquired for flying in other levels. The same principle applies to attaining aircraft, though if everything is flown under the ace difficulty in the first mission, all of the planes (except for the SR-71) will be available to you. Zip through the rookie difficulty in the second mission and all the weapons packs will also be at your disposal. The real fighting begins in mission three, once you have almost all of the planes and the weapon packs.