Why does San Francisco International seem to suffer so many more weather-related delays than airports in Oakland or San Jose?
There are two main reasons:
SFO is designed to handle up to 60 aircraft arrivals per hour in good 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.”
The problem is that planes are only allowed to land side-by-side on these parallel runways during clear weather. When inclement weather strikes, the FAA forbids parallel landings. So all planes must land in single file, which cuts the airport’s arrivals capacity in half— from 60 down to 30 or 38 per hour, depending on the severity of conditions.
And when planes arrive late, they most likely end up departing late, compounding the frustration level at the airport, and leading to poor on-time performance numbers.
When bad weather strikes and the arrival rate at SFO is restricted to just 30-38 per hour, problems arise when the number of arrivals exceeds that ceiling.
Before 9 a.m., arrival volume at SFO remains 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 over 40 aircraft per hour are scheduled to land at SFO.
So that means that if a storm blows through SFO mid-day, you can expect major delays, which will ease 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 is that their volume is low…they rarely exceed their capacity for arrivals in good or bad weather.