I've had similar experiences with Orbitz doing a southern California airport search. I think it has something to do with Sabre (the underlying engine).

Try ONT with 100 miles. I think that gets SNA, BUR, LGB, LAX, and PSP, but not SAN (which is what I usually want).

You can also try QLA, which should do just the four metro airporst (the above minus PSP), but it doesn't work with all interfaces, and can also produce inconsistent results.

In the same vein, NYC should pull EWR, LGA, and JFK, but not HPN or ISP.

More that don't exist but should:
CHI for ORD and MDW
BAY for SFO, OAK, SJC
WSH for IAD, DCA, BWI
YZZ for YYZ, YTZ