A week of steady rain has caused a steady stream of delays at SFO (Photo: Chris McGinnis)
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. On Thursday (Feb 9) the FAA is reporting delays averaging a painful three hours at SFO. According to FlightStats.com operations are normal at nearby Oakland and San Jose.
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 soggy numbers from the U.S. Bureau of Transportation Statistics: SFO ranked 28th out of 29 major airports in on-time arrivals in the first 10 months of 2016. It ranked 22nd 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.
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The West Plan at SFO allows up to 60 aircraft arrivals per hour (Illustration provided by SFO. Yes, we know about the “SJO” mistake designers made 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.
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During rainy weather, SFO switches to the Southeast plan, which slows down operations (Illustration provided by SFO. Yes, we know about the “SJO” mistake designers on this image )
If you live in San Francisco, you can tell when planes switch to the Southeast Plan because some 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.
The main reason that airports in Oakland and San Jose don’t face such on-time performance issues– even when it’s raining— is because 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.)
Last week reported on just how big that difference in volume really is: Last year, SFO handled a record 53 million passengers while Oakland had about 12 million and San Jose reported about 11 million.
In 2014, 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.
Have you or 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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Hopefully Trump will dismantle the EPA and they can build a runway with adequate distance away from the other parallel runway.
Airlines need to just bail from SFO and make the City (SFO) suffer financially, instead of the passengers suffering.
PS-Build the damm CA High Speed Rail, and get 30 percent reduction of the flights to LA out of SFO
SFO is in unincorporated San Mateo County, near the Cities of South San Francisco, San Bruno, Millbrae, and Burlingame.
SFO does get more fog than those other airports, but the part of the approach that requires visibility is the five or so miles south of the runway, essentially from the San Mateo Bridge in. As long as pilots can maintain visual contact with the runways and each other in this stretch it doesn’t really matter what’s happening north of SFO.
No it really doesn’t. The weather at SFO is usually the same as OAK or SJC. Remember SFO is really in San Carlos not San Fransisco. Completely different fog patterns over those hills.
Actually most people blame ATC
Of course most people wont’ bother to read this, and instead choose to just blame the airlines.
Thanks Chris. I’ve since retired but don’t miss those days driving in when the weather was bad. Excellent article and describes the situation at SFO well.
thanks, Soman! Always good to hear from ATC! Appreciate what you and your colleagues do for us!
Good article. Runway configurations are largely influenced by winds and precipitation. Strong winds with rain require all departures and arrivals to operate on one set of parallel runways. 28/28, 19/19, 10/10 or every once in awhile 01/01. Surprisingly fog is not a real issue at SFO, however, the marine layer pushing in from the west causes plenty of delays. Mostly in the summer and fall. Best to catch those morning flights as the article suggests. 25 years as a controller at SFO talking.
The legacy of Willie Brown. SFO had a solution, but he said no. So for decades we will pay a heavy price.
All the delays have a heavy environmental cost too.
Yea, SFO sucks in the rain. Early Jan I had to switch my flight to the one going into Oakland, no delays. Another time I was delayed out of SFO, switched to depart out of OAK.
Usually I fly between NorCal and SoCal, so those flights are the most delayed/cancelled since it’s short distance.
Great writeup, very interesting. I live not too far from the west plan approach path.
I would have thought that they would just switch to southeast plan when there are southwesterly winds, to avoid crosswinds, not just for bad weather. Why would they switch to southeast plan in bad weather if there are northwesterly winds? It seems like they do as you say, since on a recent flight during a storm we landed using southeast pattern, but there were very bad crosswinds and pilot had to abort first attempt at landing. It seems to me like the west plan would have been safer.
It’s an oversimplification to say that planes land on 28 and take off on 1, in normal conditions. In fact the heavy international planes take off on 28 as well – presumably 1 isn’t long enough, although they do sometimes land on them.
Also note that SFO has a lot more fog than SJC and OAK – that’s a factor too, as anyone in Oakland can testify to when they look across the Bay and see the marine layer over SF while they bask in sunshine.
It is possible to land side by side in Southeast Plan – FAA lists an arrival capacity of 40/hour in that condition under visual meteorological conditions.
However, the use of Southeast Plan is highly correlated with low visibility, and in low visibility aircraft cannot use simultaneous approaches to either the 19s or the 28s. It’s visibility (and sometimes crosswinds) which cause the capacity problems, not just the prevailing wind pattern.
Interesting. Surely part of the difference vs SJC (not sure about OAK) is climate – it’s not far away but quite a bit sunnier and far less prone to fog.