OK... thanks for explaining that to me... thats rough... Since I just unlocked the angry bird but cant buy any weapons yet to arm it to the teeth to shoot everything down 
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I figured that as long as I do all the missions that I can do it will turn out positive like the first months where I couldnt shoot anything down but, o well...
The early game is quite confusing, I've been through that myself many times so I can give you some tips, some of these are minor spoilers:
1. All enemy vehicle activity counts against your score, even if it happens in a region where you have no radar or interceptor coverage and can't do anything about it. This is just something you have to live with and won't be a solvable problem until many months later when you can afford to build and staff more bases.
2. In the early game your biggest concern is acquiring and arming interceptors so that you can do more than watch stuff fly past your base. Try researching and rebuilding the Little Bird that comes with your base, it's an old tech helicopter like the angry bird but it comes with a built in weapon and some ammo. If you're not sure what to do next go back and read the bootypedia entries to see what your crew has to say.
3. Try to intercept highwayman hoverpods and bandit cars as much as possible. They can drop basic craft weapons like light machineguns you can mount on your craft to shoot down more bandit vehicles, get more weapons/ammo and form a self sustaining cycle. The little bird is ideal for "kickstarting" this process because it comes with a built in chaingun.
4. To improve your early game interceptor capability put aside the shiny stuff and prisoner interrogations and focus your research on things like smithing, tools and necroplane parts. "Necroplane" parts are catch all term for low tech salvaged aircraft parts from WW2 and cold war designs, researching these will allow you to recycle them to salvage weapons and ammunition you can use to arm your craft, and later on you can build new aircraft out of these parts.
5. If things seem like you are behind the curve and won't be able to beat your score deficit, don't be afraid to just start a new campaign using the lessons you learned in the previous one.
