On certain days, depending on weather conditions, large commercial airplanes arriving to SJC fly over Sunnyvale. For safety reasons, aircraft must take off and land into the wind. When winds shift to the south, SJC operates in what is called a “south flow pattern” and uses an alternate arrival path into SJC that allows aircraft to land into the wind.
In south flow, aircraft follow a basic traffic pattern over the area to the west of SJC, taking them over Sunnyvale before they turn east over Moffett Airfield to reach the airport. Sometimes, the planes also head farther north after crossing Sunnyvale, over Mountain View and Palo Alto, before turning east over the bay.
When these weather systems change, the airport returns to its normal “north flow,” configuration, and Air Traffic Control begins directing aircraft to arrive over downtown San Jose.
The blue line indicates north and south flow into SJC. The red line indicates arrivals into SFO over the Santa Cruz Mountains. SJC aircraft must fly within the south flow corridor (any farther west would impact SFO arrivals, any farther east would not allow enough space to complete the turn into SJC). Source: SJC Airport Administration
The “south flow pattern” explains why SJC flights are over Sunnyvale at certain times. But why are we increasingly bothered by their noise? Based on historical FAA SJC flight approach data, there are several explanations for the changes, all of which concentrate and intensify the air noise:
- Increased flights into SJC, with major growth expected; based on FAA SJC radar counts, the number of SJC flights has increased by 15% January through August in 2016 compared to the same period in 2015.
- Narrowing of SJC flight paths over Sunnyvale as a result of advances in GPS/RNAV/RNP navigation.
These two figures illustrate the distribution of SJC flights over Sunnyvale in 2013 and 2016. The flights are now concentrated in a narrow flight corridor, which intensifies the aircraft noise. Source: SJC Airport Administration
- Planes flying at lower altitudes (to save the airlines time and money).
- Planes flying at faster speeds.
- Planes making steeper descents between Cupertino and Sunnyvale.
- Possible increased use of loud air brakes and flaps (“flying dirty”) due to steeper descents and faster speeds.
- Changes in weather patterns requiring more “south flow” days.
Although we cannot influence the increasing air traffic and the changes in weather patterns, we can advocate for planes to fly over Sunnyvale at higher altitudes and in wider corridors to mitigate noise levels. (For a hopeful FAA response, see this article in Air Transport World.)
If you are bothered by air noise from SJC flights, you must complain! Complaining to airport management, the Federal Aviation Administration (FAA), and our Congressman is the most effective way to mitigate air noise over our neighborhoods. The FAA’s decisions about flight paths and noise abatement will be based on the number of complaints made by Sunnyvale residents. Complaining is the best way to bring about change!
Make a Complaint
- Noise Abatement complaint form
- Through WebTrak (You can access the WebTrak complaint form by clicking on the plane on the WebTrak screen. A small window will appear with a button for “Report Aircraft.” Clicking the button opens a complaint form with information about the plane already filled in.)
(Note: For those emailing the noise office, please be advised that only complaints logged through the Noise Abatement website or through the WebTrak site are included in published data. Emails sent directly to the Noise Office are not included in official complaint data.)
If you have other questions or comments for SJC, you can email them at firstname.lastname@example.org or call the SJC Noise Hotline at 408-452-0707.
Because SJC does not report its air noise complaints to the FAA, you should also email your complaint to 9-AWA-NoiseOmbudsman@faa.gov. You will need to provide your name and address, the date and time of the noise disturbance, the type of aircraft (jet, small plane), a description of the noise issue, and the airport or official you have contacted about this event.
If you are not sure which airport the flight is using, check a flight-tracking web site (click on the tracking tab above for more information) or call the SFO Noise Office at 650-821-5100 (M-F, 8-5). The SFO office has the capability to determine the origin and destination of all air traffic in the area.
Voice Your Opinion
Call or write to your County Supervisor and Congressman and ask them to find a solution to the increasing air noise. Tell them how it is affecting your quality of life.