When your descending plane is 50 miles from the San Francisco airport, it is within TRACON airspace. An approach controller directs your pilot to adjust the aircraft's heading, speed and altitude to line up and prepare to land along standard approach corridors. Your pilot then aligns your plane with the runway. When you are 10 miles (16 km) from the runway, the approach controller passes your plane off to the local controller in the airport tower.

Photo courtesy Federal Aviation Administration (FAA)
Departure and approach corridors for eastward air traffic to and from airports in the San Francisco Bay Area TRACON airspace. (Click on the image for a larger view.)

FAST Software
The approach controller uses another software program developed by NASA and the FAA called the final approach spacing tool (FAST). The FAST program assists controllers in choosing the landing order and runway for each approaching aircraft. The program does the following:
  • Projects each aircraft's flight path based on flight plan and radar tracking
  • Predicts arrival time
  • Suggests landing order and runway assignment based on calculations that take into account aircraft size, aircraft performance capability and wind directions
The FAST software helps to ensure that no single runway or controller gets overloaded with planes, helping to minimize unnecessary delays.