The question was brought up on the forums and clarified by Spartan Mike, though I realize at this point I can't actually back that up since the forums are down and anyone can make that claim. (Anyone tried the page caches on some search engines to see if much could be recovered?)
I'll paraphrase a bit since I can't remember the exact wording.
A SAS can only be rebuilt if a SAS is completely destroyed. [key there is SAS, not SAW] And that you have to have enough SAW in your graveyard to build the new SAS unit.
So if you have 6 SAS units, lets say 3x5 fighers (Local air support), as well as 1x3 and 2x4 from carriers. You could loose 1 SAW from each unit, and therefor have 6 in the graveyard, but you can't rebuild yet because no SAS unit has been destroyed. If the 1x3 unit is wiped out completely it could be brought back as a 1x4 with the larger carrier (as long as at least 4 SAW are in the graveyard). And the same way if a 1x5 (local air support in this example) is destroyed it could only be brought back as either a 1x3 or 1x4 because that is all the carriers can output.
Also in the rules clarification, the rules state CAP has to come from local air support and therefor has to be fighters. He said that carriers can't re-task CAP, they have to stay fighters.
edit: so I was mistaken, it was Spartan Josh. And yes, a decent amount of the forums are cached, no idea how long it will last but if there is something you have to find, I would find it sooner rather than later.