can't build air units

[MCB]

i have oil, hell i have built a carrier, now i'm about to go to war becuase of a defensive pack but i'm not intrested in using land units, i just want to bomb them and let my allie take the cities but i can't build any air units. what em i missing here?

 

[Finite Monkey]

I'm going to ask some simple questions so slap me if its not the issue (hopefully this will rule out gameplay issues)

1. Does the oil have an Oil Well/Oil Derreck on it linking it to your empire.
2. When you consult the Tech advisor about flight and you hover your mouse over the Airplane Icon are all of the prerequisites met? (Techs and Resources?)

Now for an odd question (it has happened to me)

3. Did you inadvertently trade your only source of Oil to an AI ally? I traded my only source of Iron once and I had to stop producing swordsmen. Why do they allow you to trade it if its your only one? Now I consult the advisor to look at my resources more closely.