One time I was driving between LA and Provo and I was out on the I-15 in the desert somewhere. I saw one of those "patrolled by aircraft" signs and happened to notice a small plane flying overhead. It was doing large figure 8's, so it got me curious. About 30 seconds later two cars went flying past me (they probably knew each other because they were driving alongside each other). I let them get a ways ahead of me, then started to speed up...basically I was using those guys as rabbits to flush out the cops if there were any. Well as soon as we passed by the next offramp, two cops were apparently just sitting up there waiting for the two cars in front of me to come flying by. The cops came flying down the offramp right as the two cars were speeding past and they pulled both those guys over.

The fact that the plane doing figure 8's over this stretch of the freeway and that two highway patrol officers were just sitting there waiting for the two speeding cars to come by tells me that the airplane was radioing down to the cops when he spotted speeding cars. First time I'd ever seen something like this. It does not seem very economically efficient at all, but I guess the "patrolled by aircraft" signs are more than just a threat.