Welcome to the tracking world
Wikipedia lists Air Transport International doing DOD contract work. It could be those are stops on a muliti hop delivery flight.https://en.wikipedia.org/wiki/Air_Transport_International
I'm just across the lake in El Dorado hills and built a 978 cantenna but, being down in the valley, I got very little traffic.
A cantenna or spider are quite easy to make quickly. A colinear is easy to make, and easier to make badly. Details can be found at http://discussions.flightaware.com/ads-b-flight-tracking-f21/three-easy-diy-antennas-for-beginners-t20177.html