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4 Answers

What is “Flow Control”?

Asked by: 9164 views General Aviation

I'm in Eugene, Oregon.  What does it mean when the local ATIS says "Flow control to San Francisco"?

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4 Answers



  1. Scott on Mar 28, 2012

    It basically means that there’s too many flight plans in the system all timed to arrive at SFO at the same time, and that ATC will need to start assigning times to spread out the arrivals into that area, such that the airspace and runways can all accomadate the arrivals/departures in the area.

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  2. Bill Trussell on Mar 28, 2012

    This is a good example of the type of information pilots are expected to be familiar with under the following FAR
    91.103 Preflight action. Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight. This information must include—
    (a) For a flight under IFR or a flight not in the vicinity of an airport, weather reports and forecasts, fuel requirements, alternatives available if the planned flight cannot be completed, and any known traffic delays of which the pilot in command has been advised by ATC;
    Flow control is the result of several automated systems that look at a lot of information including known traffic and weather conditions and suggests actions to be taken to make it so that airborne holding is not required. Gate holds are the preferred method of addressing capacity issues as it is safer and more fuel efficient.

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  3. John Parsons on Mar 28, 2012

    Ah, so when a pilot hears “flow control for San Francisco” in the ATIS announcement, he can expect to possibly wait some extra time on the ground before receiving takeoff clearance, because ATC isn’t going to have him take off just to head into a big stack over SFO.  Is that the idea?

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  4. Scott on Mar 29, 2012

    John, basically yes, It saves fuel and is easier to hold people on the ground than to hold them in the air. Far more planes can be separated on the ground than in holding patterns. Also, there are several layers of flow control, ranging from just a quick call for release, to EDCT times, to Ground Stops, to Gate holds. Each are just various levels of managing the traffic in a specifc area. Most of these are for an actual airport, but occasionally there’ll be EDCTs for just enroute sectors, since there’ll be way too many planes in a specific center sector at a single time and they issue EDCTs or force reroutes(or this is a way pilots can avoid the times if they’re really bad).

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