Flight delays at San Francisco International Airport regularly exceed two hours when it’s rainy, windy or foggy, while airports in San Jose and Oakland report few if any delays. As I write this, the FAA is reporting delays averaging 3 hours 40 minutes at SFO.
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 27th out of 29 major airports in on-time arrivals in the first 10 months of 2014. It ranked 18th out of 29 in on-time departures (an improvement over 2013 when it ranked 23rd).
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.
The West Plan at SFO allows up to 60 aircraft arrivals per hour (Illustration provided by SFO. Yes, we know about the “SJO” mistake on this image.)
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 figure) During 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).
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.
Related: Is this the best flight of the year?
During rainy weather, SFO switches to the Southeast plan, which slows down operations (Illustration provided by SFO. Yes, we know about the “SJO” mistake on this image )
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.
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.
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Guest says
December 15, 2014 at 11:37 amThere is another way to fix the runways… talk United into closing its maintenance base. Of course, it is the single largest taxpayer in San Mateo County and its closure would devastate the local economy… but The City only listens to its own agenda, not to a regional agenda. As I have said before, SFO needs to be taken over by a regional board that will have San Mateo County representation. This would clean up the misconnection between the airport and Millbrae BART (which is shut down early, unjustifiably) and reopen bidding for airport businesses that have been forced to pay off Supervisors and serve organic food.
tommy says
December 12, 2014 at 10:08 amI also would mention that foggy is worst in the winter than in the summer as people would normally assume. So this also contributes to delays during the year.
oaygc says
December 11, 2014 at 7:59 pmMore: ACV (Arcata-Eureka) airport was INTENTIONALLY placed iduring WW II in the foggiest place in the USA to develop landing practices in foggy areas—England—where bombers and other planes took off for Europe. Foggy ACV to foggy SFO (no plane service to OAK or SJC). It’s a multiple gamble. (good wi-fi in the Arcata airport though…)
Recently, SkyWest/United announced it will soon cease its longtime Arcata-Saccramento run altogether. AND SkyWest says they’ll soon start flying jets into Arcata and cut back the number of flights because of the jets’ increased capacity (to say nothing of SkyWest’s financial troubles). Some people from here drive to Medford (or Santa Rosa) to pick up planes directly to LA or elsewhere. We love it up here, although sometimes not so much.
(Do you want to add roads sliding out into this discussion? Didn’t think so.)
Alleycat078 says
December 11, 2014 at 7:54 pmAnother way to understand “why the planes whistle and moan” When the wind shifts the landing approach and take off are reversed ie: 180 degrees out, so if you live in the city will be under the landing pattern and you are hearing what aircraft sound like on approach.
Chris McGinnis says
December 11, 2014 at 7:06 pmThanks, Justin! –chris
Justin says
December 11, 2014 at 7:01 pmThe missing detail about which runways are in use is this: airplanes want to take off and land INTO the wind — when you fly into the wind, more air passes over the wings at a given ground speed, giving them more lift. So if you want to land an airplane at 150 knots airspeed (enough air over the wings to keep it flying, but slow enough to be under control) and you have a 20 knot headwind, you’re only moving at 130 knots relative to the ground. With a 20 knot tailwind, you’re moving at 170 knots over the ground, a much harder landing to pull off.
In non-stormy weather, the prevailing winds on the bay mean planes fly roughly into the wind by landing on runways 28 (~280 degrees i.e. westerly) and taking off from the 1s (~10 degress, i.e. northerly). Typical stormy weather means landing on the 19s and taking off on the 10s to fly into the wind.
The arrival and departure patterns in the diagrams just show the choreography required to get planes on and off the ground on headwind runways at the 3 airports. The planes are always “whining and moaning,” it’s just they’re doing it over your house when the weather puts them in that traffic pattern. Normal traffic patterns are over the bay for SFO departures and arrivals.
Dave says
December 11, 2014 at 6:33 pmSame issue as oaygc; I originate and return to ACV so SFO is the only game in town. United Express/Skywest used to offer limited service to/from Sacramento twice a day but that wasn’t very useful — and returning if you missed the one connection to ACV you were stuck.
Dan Leifker says
December 11, 2014 at 1:30 pmWith the new AirBART think in Oakland, I plan to switch and use OAK from now on whenever possible. It’s not a glamorous airport, but who cares if the planes take off and land on schedule?
Vallman says
December 11, 2014 at 12:54 pmI fly A LOT. I learned years ago to avoid SFO even in clear weather. True there are more direct flights (but SJC and OAK have more these days). But I’d rather wait at home for an on time direct, park for less and have a better chance to arrive on time. What is the use of getting an early flight if it is delayed and you’re sitting at the airport bar?
Chris McGinnis says
December 11, 2014 at 11:37 amThanks! Not sure about the whistling and moaning but maybe one of our more technical avgeek readers could explain? I’m hearing them moan overhead as I write this in Noe Valley. — chris
kevin says
December 11, 2014 at 11:33 amThis is FASCINATING. Thanks for posting this explanation. Can you please elaborate on how and why the planes whistle and moan on the SE plan? I can’t say I’ve noticed it myself, but I want to be on the look out!
oorfenegro says
March 1, 2014 at 2:44 pmDon’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 says
February 13, 2014 at 1:06 pmUnless 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 says
February 11, 2014 at 2:19 pmI 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 says
February 11, 2014 at 12:21 amWhile 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:
http://www.flysfo.com/community-environment/noise-abatement/file-a-complaint
MDR says
February 10, 2014 at 10:42 pmThe 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.)
Chris McGinnis says
February 10, 2014 at 2:34 pmAn 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 says
February 10, 2014 at 1:39 pmThe 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.