I did wonder about the OP’s question. In the L.A. area, it’s been ten years or more since I’ve seen either the “Patrolled By Aircraft” signs or the planes overhead, and before then I used to see them all the time.
Has the focus of the airborne patrol been shifted to rural areas where it’s usually easier to speed?
There was a guy out here (or was it wisconsin) that got tagged for going 200+ mph on his motorcycle by a police airplane. The person who calculated that speed stood firmly by his estimate. Last I read, the bike was modified, but not sure if it was enough to attain such a speed. Did a half-assed search for the article but couldn’t find it. It was a couple months ago I believe.