During times of inclement weather, some mornings, or during frontal passages, the wind at SJC will blow from the south. For safety reasons, aircraft must take off and land into these southerly winds, requiring the airport to operate in "south flow," an alternate arrival path into SJC that allows aircraft to land and take off into the wind. During these times, aircraft must follow a basic traffic pattern over the area to the west of SJC over Santa Clara and Sunnyvale, before turning east over Moffett Airfield to return to the airport. As these weather systems pass the airport returns to "north flow," our most common configuration, and Air Traffic Control begins directing aircraft to arrive over downtown San Jose.

Arriving aircraft at low altitudes are generally quieter than departures of the same aircraft type because this mode of flight requires much less engine power, which is the dominant source of airplane noise.  However, close to the airport, the relative quietness of arrivals may be offset by the fact that the airplanes are typically lower in altitude than departures over the same location.  Configuring the plane for landing requires the pilot to lower the landing gear and wing flaps which enables the airplane to slow down and the wings to generate greater lift. However, the noise generated by the turbulent airflow over the landing gear and flaps also creates substantial noise that can equal or exceed that produced by the jet engines.  The turbulent airflow also increases the drag on the airplane requiring the pilot to increase engine power to maintain a safe descent path to the runway, which also increases noise. 

The City does not have direct authority over air space. We are, however, working with regional agencies and federal representatives and authorities to mitigate the effect on our residents. The authority to control aircraft in flight and on the ground is vested exclusively with the Federal Aviation Administration (FAA).