COIN Aircraft?

[jivemi]

Pardon my ponderous stupidity, but what exactly does "COIN Aircraft" refer to? In the game manual it says,

"UnitClass 223=COIN Fighter Plane
Clone of Fighter-Bomber, but it is less vehicle-centric in its targetting, so is more useful against them"

The only independent reference that makes sense (to me anyway) is "Counter-Insurgency Aircraft," which would seem to imply it's useful against infantry, not vehicles. Thanks.