ok overall 4/5 helicopter are a pain, the crashing system needs some improvement, and also after you get all the tier 3 upgrades you should be able to purchase 1 and only 1 tier 4 upgrade.
i.e tier 4 windshield not damaged by soldier weapons and regular zombies, tier 4 Bumper run through small cars without the strafing but keeping the damage, and other buffs that would not break the game.
3/5 not a bad game it could use upgrades, purchasable aliies, and maybe different kinds of strikes (i.e. air or armored bombardment) but overall a decent time killer.
 "Road of the Dead"){kind=icon}
 "D-Day Defender"){kind=icon}
 "Obama Versus Aliens"){kind=icon}
 "Crush the Castle"){kind=icon}
 "Ninja Vs. Pirate"){kind=icon}
 "The Great Sperm Race"){kind=icon}
 "Bot Arena 3"){kind=icon}
 "Epic war"){kind=icon}