Agents at the Air and Marine Operations Center in at an Air Force Reserve base in Riverside, Calif. track 20,000 to 25,000 flights a day for suspicious activity. Master Sgt. Julie Avey/AMOC hide caption itoggle caption Master Sgt. Julie Avey/AMOC National Security Unregulated Skies: Keeping Watch On America's Vertical Borders Tens of thousands of private planes fly through U.S. airspace daily. Federal agents at a Southern California air base monitor those flights, looking for drugs or terrorists. Sometimes, they find them.