This was how I heard that there was no air cover. They had to scramble fighter jets from down around L.A.
I would think that of all cities (after NYC, WA D.C., Chicago, and L.A.) that San Francisco would be getting air cover. That must mean that no one other than those four have it.
Still the explanation for the "buzzing" was never made publicly clear; supposedly soomeone just taking photos. I think in this area, the last thing politicians want is a public demanding answers, for all of their moaning and groaning about Sunshine laws.
Furthermore, Hamilton AFB in Novato was closed, making the area closest to the Bay more vulnerable.