The Federal Aviation Administration announced ground delay programs for San Francisco International Airport on Thursday because of low clouds and shifting winds affecting aircraft movements.
The reduction in aircraft movements at SFO started at 8:27 a.m. and will last until 11:59 p.m., with delays estimated to average three hours and affecting all flights in the contiguous U.S. and those from Calgary, Vancouver, and Edmonton.
A ground delay program by the FAA limits the number of aircraft arriving or departing in certain time frame. Flights scheduled to fly to affected airports are often held at their origin until an arrival slot is approved by air traffic controllers.
The restrictions are meant to prevent aircraft from holding in the air where they burn extra fuel and in rare cases reach low fuel levels. It also reduces the workload on air traffic controllers who have to properly space aircraft as they move through one of the busiest airports in the country.
SFO will limit 25 landings an hour before increasing to 36 as weather improves.
Airport spokesperson Doug Yakel said just before noon, 312 flights experienced a delay, about 27% of all flights, and 39 flights have been canceled. Delays were averaging 65 minutes but could increase.
“This delay program is due to unusual wind conditions; coming out of the east, which have required a change to how aircraft take off and land, to a less efficient configuration,” said Yakel.
Conditions at the airport mean aircraft are approaching from the west, over U.S. Highway 101, as they land on runway 10L. Typically planes land from the complete opposite direction, over the Bay.
Oakland San Francisco Bay Airport experienced minor delays and San Jose Mineta International Airport has not experienced significant weather interruptions.
Passengers are urged to contact their respective carrier for more information.