Tip: Stormy weather slowing you down? Here’s why…

(Photo: SlightlyNorth / Flickr)

Flight delays at San Francisco International Airport exceeded two hours throughout our recent rainy weekend, while airports in San Jose and Oakland reported few if any delays. Here’s why:

As most frequent travelers know, delays mount at SFO almost every time a storm blows in off the Pacific. Just look at these sad numbers from the U.S. Bureau of Transportation Statistics: SFO ranked 28th out of 29 major airports in on-time arrivals in the first 11 months of 2013. It ranked 23th out of 29 in on-time departures.

Why does SFO seem to suffer so many more weather-related delays than other airports in the Bay Area?

Of course, the answer is endlessly complicated, but for the most part, the main reason is capacity. SFO’s runways are too close together to allow simultaneous operations during wet weather. Due to environmental concerns, there are no current plans to further separate the runways, which would require expansion into the Bay.

SFO Plan West

The West Plan at SFO allows up to 60 aircraft arrivals per hour (Illustration provided by SFO)

SFO runways are designed to handle up to 60 aircraft arrivals per hour in dry weather. That’s because the airport operates two sets of parallel runways– one set for takeoffs, the other for landings. These parallel runways intersect at their midpoint forming a giant “X.” (See figureDuring dry weather, two streams of planes can land and take off from these parallel runways.

The problem is that planes are only allowed to take off and land simultaneously on these parallel runways during clear, dry weather.

When storms blow in, air traffic control changes up the formation in which planes land, from the dry weather “West Plan” (with aircraft arriving on runways 28L or 28R and departing on runways 01L or 01R– see above) to the stormy weather “Southeast” plan (when aircraft arrive on 19L & 19R and depart on 10L & 10R– see below).

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When air traffic controllers switch to the Southeast plan, simultaneous operations on parallel runways is forbidden, which cuts the airport’s arrivals capacity in half– from 60 down to 30 or 38 per hour, depending on the severity of conditions. All planes must land in single file, which causes delays when there are 60 planes scheduled to land, but air traffic control only allows 35. And when planes arrive late, it’s likely that they will also depart late.

During rainy weather, SFO switches to the Southeast plan, which slows down operations

During rainy weather, SFO switches to the Southeast plan, which slows down operations (Illustration provided by SFO)

If you live in San Francisco, you can tell when planes switch to the Southeast Plan because arriving aircraft whistle and moan as they descend through the clouds over the city as they approach SFO.

What can you do to avoid this? Fly early during storm season. Before 9 a.m., arrival volume at SFO is below 30 per hour. But after 9 a.m., just over 30 aircraft are scheduled to land. The arrivals rate peaks between 12 noon and 2 pm when 40+ aircraft per hour are scheduled to land at SFO. The situation usually does not improve until later in the afternoon when arrival volume falls below 30 per hour.

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The main reason that airports in Oakland and San Jose don’t face such on-time performance issues– even when it’s raining–  is that their volume is low. They rarely exceed their capacity for arrivals in good or bad weather. (For example, neither airport is included in the BTS’s top 29 airports cited above.)

Late last year, SFO announced that new landing procedures could help reduce delays– but those new procedures only apply during periods of low ceilings (fog) but not rain. Expect even bigger delays when SFO shuts down two runways for safety related upgrades during the upcoming peak summer travel season– mid-May through the end of September.

Would you consider switching your flying to Oakland or San Jose due to delays at SFO? Why or why not? Please leave your comments below. 

– Chris McGinnis

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  • oorfenegro

    Don’t have a problem with SFO since they have more non stop flights than every other Bay Area airport, particularly to the nation’s largest cities. Better to be delayed at SFO on a non stop than to leave on time from Oakland or San Jose and to delayed or stuck overnight at a connecting hub in Denver, Chicago, Dallas, Houston, Atlanta, Charlotte or Phoenix.

    Also two of the three domestic SFO terminals are less than three years old and has been designed to get in and out of security quickly, there are a million electrical outlets and many restaurants and bars of all budgets to get a bite to eat and something to drink, and to kill time when flights are delayed.

    Also every major airline flies out of SFO, and with the exception of Southwest, the airlines are consolidating out of SFO with every merger. Since United merged with Continental they’ve eliminated flights out of Oakland and only have a few flights out of San Jose and word is that as part of American’s merger with US Air they are going to do the same thing with San Jose and Oakland.

  • Paige Graham

    Unless it’s a last minute flight and that’s the only departure available, I do not fly out of SFO. I hate it. I hate paying the bridge toll to get there, I hate that circus they call a campus, and I hate trying to find anything there. I almost exclusively fly out of OAK and occasionally fly out of SJC, they’re both just much less hassle overall.

  • Jason R

    I have effectively stopped flying out of SFO unless it is for transcon or international flights. Most of my flying is regional, and I got weary of cancellations and delays at SFO many months of the year. I tend to fly early am, and at that time of day I can get to OAK almost as quickly as I can get to SFO. So OAK and SWA probably get 45 of my 50 flights a year.

  • sweatpants

    While I usually fall on the side of caution with environmental matters, I think a few more meters of fill in the bay at the airport would be a huge benefit to many in the bay area. How ridiculous is it that a city known for its fog its airport’s usual landing runway can’t handle foggy conditions? The southeast plan sends the landing planes low enough to notice each one right over my neighborhood just east of Lake Merritt in Oakland. This is the first time I’ve noticed myself being a NIMBY, but it is a pretty big backyard getting buzzed, compared to the usual landing path over the water.
    By the way, it is easy to log a noise complaint to SFO online here:

  • MDR

    The two plan diagrams shown here are the best illustrations I’ve seen of the airspace around the three main Bay Area airports. (Nitpick: “SJO” should be corrected to “SJC” in the legends.)

  • http://www.travelskills.com/ Chris McGinnis

    An interesting post script to this post from an Air Traffic Control insider who follows The BAT:

    Each of our two plans has several different runway configurations, based on wind direction and speed:

    West Plan

    Land 28s, Depart 1s – What we use 75% (or more) of the time

    28 Shoreline – Strong winds from the west (above 25knots); also what we’ll use all summer, as you alluded to

    28 Straight-out – Rare, used when Oakland must land Runway 12 due to wind on that side of the bay

    Land & Depart 1s – Used it briefly a couple weeks ago, but very rare circling visual approach

    Southeast Plan

    Land 19s, Depart 10s – Most common with south/southeast winds as storms pass through

    Land & Depart 19s – Used during periods of high winds from the south (e.g. frontal passage) that exceed crosswind component for the 10s — used for several hours on Saturday.

    Land & Depart 10s – Rare, used with strong winds from the east. We used it for about an hour a couple weeks ago.

  • oaygc

    The following comment is as much about SFO as it is about other airports and carriers:

    People from some airports MUST land at SFO and CANNOT choose another airport because the (only) airline serving them only lands at SFO. I fly out of the Arcata/Eureka airpot (ACV); only United Express flies to and from here and only to SFO. Some people up here drive to Santa Rosa to catch another carrier to Los Angeles or other destinations.

    In inclement weather—there is no better or worse time of year— the more reliable and less troublesome tactic is to try to fly out of ACV early in the morning; arriving here is another matter. However, coupled with the foggy conditions here and the situation at SFO, travel to and from here is always dicey. We really appreciate the persistence of United Express for coming and staying here all these years. Right now the ACV glide slope indicator is out (remember Asiana…?), so this adds to the problems here until that’s fixed, but the ceiling minimums are higher until it’s fixed.

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