Problem with the state of the armed plane is they double-nerfed it. It's essentially useless against anything that moves. Only stationary targets are vulnerable, and even then, not very.
It went up in price and instead of shooting like a normal gun with some bullet spread, it now shoots like a laser. Imagine trying to hit a target with an IR laser from a caesar, because that is what the armed plane is now. Either leave the price alone, or revert to the old gun.
Bad game design is reflected in abrupt changes like this. If you're going to stick with the changes, you might as well just remove the damn thing. It's pretty useless as is now.