All Terran and Zerg units are viable barring the BC.
The only viable Protoss air is the Void Ray. Phoenix are horribly limited, and you gotta be pretty ballsy to bother building Carriers and the Mothership. I mean, you could "technically" include the Observer and Warp Prism as part of their air force but pushing it. Its still only 1/2 of their force they can use on a regular basis to any worthy effect.






