Bullfrog

Short and squat, with plenty of cargo room. Famous for making Skyrates very wealthy without drawing too much attention. All that, and the Bullfrog kind of looks like he has a face. Cute, isn't he?

Combat versus the Bullfrog
It's quite dangerous to approach the bullfrog from either the front or the back, as both carry heavy firepower. That said, the sides are exposed and none of the bullfrog's guns swivel. Go for the side, but be wary of the arcs.

Fighting in the Bullfrog
With the advent of upgradable plane customization, there is the possibility of making the bullfrog's respectable speed outright silly for a trading aircraft. It's then possible to simply chase down combat planes (and some performance planes!) with precise use of afterburners and cornering. That said, one possibility is to equip the Bullfrog's front guns with flak or autocannons (or both!) that will easily overlap and shred low armored planes to pieces. The rear arc, meanwhile can be purposed to taking down bigger fare by equipping it with a howitzer. Throw a quality barrel extension and armor piercing rounds in the mix and even Leviathans will fall without too much effort.