Northern California TRACON (NCT) (Terminal Radar Approach Control), or NorCal TRACON for short, is an air traffic control facility that provides safety alerts, separation, and sequencing of air traffic arriving, departing, and transiting the airspace and airports in Northern California. Located in Rancho Cordova near Sacramento, NCT controls airspace over 19000 square miles, and serves Reno International Airport, Sacramento International Airport, San Jose International Airport, Oakland International Airport, and San Francisco International Airport, plus 19 other smaller airports with air traffic control towers. NCT is the 3rd busiest TRACON in America. NorCal TRACON is the step between local control (in an airport's control tower) and Air Route Traffic Control Center (ARTCC), in this case, Oakland Center (ICAO code: ZOA). San Francisco International Airport is the 2nd largest airport in California and the largest airport serving Northern California.
Directing planes to their destinations: When an arriving aircraft nears the Bay Area, ZOA advises it to contact NorCal TRACON. TRACON gives the arrival a descent profile, ILS and other landing aid clearances. During busy times, TRACON often has to hold aircraft in the air. After TRACON sets up the flight for an approach to landing, the flight contacts the tower at the arrival airport for landing clearance.