Z2Live is the Seattle-based developer behind the popular freemium Trade Nations title for iOS, and the company's latest release is another freemium app called MetalStorm Online. As you can see from the picture above, it's a combat flight simulator, which has you piloting a series of jets through the air and trying to take down enemies both real and computer-controlled.
It's relatively simple, so flight buffs will be disappointed with how superficial the game is, but as an arcade flight simulator, I liked it. The plane is controlled by tilting your iPhone and tapping or swiping on the screen to fire or perform flight maneuvers, making for a simple but satisfying combat game. It's all freemium, so you can earn coins by playing (or buy them with in-app purchases), and then use those to upgrade your plane or its various components.
You can play a versus match online with friends or strangers, and it worked surprisingly well for me when I played with a random person over Wi-Fi. You can also try single player against waves of enemies, or play co-op with a friend. Yes, the in-app purchase notices are annoying, but there's a fun flight shooter here even without spending a dime. MetalStorm Online is free in the App Store right now.