Armor Class

Each point of Armor Class subtracts one from the damage opposing shots do. You could think of Armor Class as being stopping power, hardness, impact resistance, structural integrity, armor factor or absorption (all of these have been proposed as potential renames for "Armor Class"). In Combat, the effect of Armor Class can sometimes be seen as bullets pinging off your plane (or your enemies' planes).

To minimize this pinging off effect versus enemy planes, the most effective method may be to maximize the percentage chance that your gun will fire a Critical Hit by using a gun with a high "Crit Chance" (such as a Flak Tube) and/or a Gun Mod with a high "Crit Chance Modifier" (such as Explosive Rounds). Note that Critical Hits bypass the Armor Class of any plane.

You could also increase the amount of Damage Per Second that your guns do by either selecting guns with high Damage values or using Gun Mods that increase Damage (such as Armor Piercing Rounds).

You can also protect your plane against damage with Armor Class mods, as well as any native armor class that particular aircraft has (most Trade planes have Armor Class values greater than zero, as well as a few Combat and Performance planes such as the Hades and Cetacea). Wood-Reinforced Hull mods improve your Armor Class by 5, preventing all non-crit damage by Autocannons, and Steet-Reinforced Hulls add 12 points of Armor Class, enough to protect against small Machine Guns as well. The two mods together form a potent defensive combo able to stop even large Machine Guns, but are almost worthless against Howitzers and Flak Tubes.