Once you find good ways to deal with early air, a cloaked banshee rush becomes pretty much the only practical early air move, because anti air units and detection is needed, and as a terran you can turtle easily enough that they can't take advantage of your teching.
Zerg should either invest in spore crawlers or hydras early on, though.
Alternatively, scout around.
As a rule of thumb for terrans, 5 marines will counter 1 early air unit such as a void ray.
Also, this has reminded me of an interesting strategy I saw a while back: phoenix spam which lift units into the air and then destroys them.