San Francisco International Airport (SFO, KSFO) serves San Francisco, USA and has 4 runways. Below you can see the latest wind and weather report, how that wind lines up with every runway end, and what the layout means for how the airport works.
The runways fall into two groups, running north-west to south-east and north-east to south-west. With two directions to choose from, one group usually points reasonably close to the wind. Headings are true (not magnetic), so they differ from the runway number by the local magnetic variation.
| Runway | Length | Width | True headings |
|---|---|---|---|
| 10L / 28R | 3,618 m (11,870 ft) | 61 m | 118° / 298° |
| 10R / 28L | 3,469 m (11,381 ft) | 61 m | 118° / 298° |
| 01R / 19L | 2,640 m (8,661 ft) | 61 m | 028° / 208° |
| 01L / 19R | 2,332 m (7,651 ft) | 61 m | 028° / 208° |
Aircraft take off and land into the wind whenever they can. A headwind slows the ground speed at touchdown, shortens the runway needed and gives better control. A tailwind does the opposite, so airports normally limit it to a few knots. A crosswind (wind across the runway) is harder on the pilots, and large jets have a limit on how much they can accept.
Each runway has two ends, numbered by compass heading divided by ten, so 27 points west and 09 points east. The same strip of tarmac is used in either direction depending on the wind, and parallel runways add L, C and R (left, centre, right) to tell them apart.
SFO has two pairs of crossing runways, and each pair is only about 750 ft apart. Aircraft can land on both at once in clear weather, but in low cloud and fog the spacing is too tight for simultaneous landings, so the arrival rate drops and delays build. A Precision Runway Monitor, a high-update-rate radar, is what allows close parallel approaches like these. The prevailing westerly wind makes runways 28L and 28R the usual landing runways.
AeroGaze can't see air traffic control's runway plan. It shows the latest wind from the KSFO METAR set against each of the 4 runways: aircraft take off and land into the wind where they can, so the runway ends with the strongest headwind are the likely candidates. Noise rules, traffic and the forecast also play a part, so treat it as a guide, not a fact.
San Francisco International Airport has 4 runways: 10L/28R, 10R/28L, 01R/19L, 01L/19R. The runways fall into two groups, running north-west to south-east and north-east to south-west. With two directions to choose from, one group usually points reasonably close to the wind.
Runway 10L/28R, at 3,618 m (11,870 ft) long and 61 m wide.
There is no single limit. Each aircraft type has a demonstrated crosswind figure, commonly in the range of 30 to 40 knots for large jets, airlines set their own limits (often lower on wet or contaminated runways), and the pilots decide on the day. When a strong wind blows across the runways at San Francisco Airport, you see more go-arounds and diversions.
From the METAR reports that NOAA's Aviation Weather Center publishes for KSFO, refreshed about every ten minutes. A METAR is usually issued once an hour, and sooner if conditions change, so the observation time on the page shows how fresh the report is.
They are flight categories based on cloud height and visibility. VFR: cloud base above 3,000 ft and visibility over 5 miles. MVFR (marginal): 1,000 to 3,000 ft or 3 to 5 miles. IFR: 500 to 1,000 ft or 1 to 3 miles. LIFR: below 500 ft or under 1 mile. The lower the category, the more spacing between aircraft and the more delays.
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Sources: wind and weather from the NOAA Aviation Weather Center (METAR). Runway coordinates from OurAirports (public domain); runway notes are editorial. AeroGaze is an independent site, not affiliated with any airport or air traffic service.