Air Assault is a relatively unremarkable arcade game in which you fight "invading Russian/Afghanistan forces" in Afghanistan with "Anti-Air and Mortal" (presumably "mortar") guns.
Every game begins with a slowly scrolling text introduction set to "Flight of the Valkyries," which you can thankfully skip. It outlines a muddled, quasi-historical backdrop with dubious references to "September 11" and Operation Enduring Freedom (which isn't helped by later appearances of apparent suicide bombers and oil-production fields, something that Afghanistan is not particularly known for). The game's wide-screen interface has you shooting from a gun emplacement on the lower left, alternating between a machine gun (for aerial targets) and mortars (for ground targets) with a quick tap. You shoot by tapping where you want to fire that while straightforward for the machine gun, requires some calculation for firing the mortar. As with similar games that use this same control scheme, the most accurate way to aim--tapping directly on enemies--also obscures your view. This interface can also make the onscreen pause and airstrike buttons a little unresponsive.
Your emplacement has a health meter, with three lives, and you shoot at attack helicopters (with occasional parachuters), troop-transport helicopters that drop off ground fighters, and later snipers, tanks, jets, and more. As you take out enemies, you build up a power meter for a slightly delayed, screen-clearing airstrike. Once you've completed a short series of levels, the game ends, although Air Assault does log your high scores (with Open Feint support) and you can replay at three different difficulties.
Overall, Air Assault is a pretty lightweight game that's rough around the edges, but if you don't mind its reductive take on current events, it's a reasonably fun download if you can find it for free.