Zombie Air Force Upgrades Guide
Credits in Zombie Air Force go two directions: into your plane, or into the lobby upgrades that support it. Spend them in the wrong order and every wave takes longer than it should; spend them right and your clear speed compounds until the next zone opens up. This guide lays out the upgrade priorities that hold from the first session through The Wastelands, and the thinking behind them.
The upgrade principle: damage buys time, time buys Credits
Every zombie kill pays Credits, so the only real economy in the game is clear speed. Upgrades that end waves faster pay for themselves; upgrades that do not are purchased with farming hours. That single principle sorts the lobby: damage-oriented upgrades come first, survivability second, and anything that touches neither is a late-game luxury.
Concretely, the first Credits after your starter plane go into your aircraft's damage output — the lobby's aircraft and weapons upgrades exist to make every pass over the horde kill more. The difference shows immediately: a wave that took two strafing runs takes one, and your per-minute income climbs without changing zones.
When defenses earn their Credits
Ground defenses — the barricade-side tools that shore up your position — are the second purchase tier. Their job is converting leaks into non-events: the wave that would have breached your position instead stalls against defenses while your plane finishes it. Buy your first defensive upgrade when you notice waves regularly reaching the ground in your farming zone, not before. In a zone you outgun, defenses are dead Credits.
As zones toughen, defenses graduate from insurance to strategy: a sturdy ground game lets you gamble on higher-wave clears for bigger payouts, because the cost of a mistake is absorbed instead of fatal. The zones guide covers when that math starts favoring the push.
Pairing upgrades with your aircraft
The lobby upgrades and the aircraft ladder work as a pair, and the pairing rule is simple: upgrade what you fly. Every airframe favors a style — machine-gun airframes reward fire-rate and coverage upgrades, rocket airframes reward damage and splash. Pushing the wrong stat leaves the plane feeling worse after spending, which is the tell you bought against your own airframe. When you step up to a new plane, re-check your upgrades against its strengths before your next purchase; the aircraft guide breaks down what each tier favors.
Boosts and codes: the free upgrades
Two upgrade sources do not cost Credits at all, and both should be maxed before any lobby purchase. The boost stack — group membership, the game like, and Premium — adds +10% coins each, stacking to +30% on every kill for the rest of your account's life. Active codes hand out thousands of Credits plus timed multipliers; the current pair is on the codes page and gets rechecked after every Saturday update. Redeem both before a farming session and your effective income runs a third higher with zero grind — that surplus is the fastest "upgrade" new players can buy.
The order that works
To summarize the priority chain the guide keeps returning to: codes and boosts first, because they are free. Aircraft damage second, because clear speed is income. A first defensive tool third, once leaks start. Aircraft step-ups interleaved from there, with defense depth rising as your zone difficulty does. Save Cosmetic-tier purchases for last — they fly the same routes at the same speed. Follow that chain and every Credit you spend shows up in your per-hour income, which is the only scoreboard that matters in Zombie Air Force.