"It should help a little bit during the bad weather," airport spokesman Doug Yakel said.
Yakel explained that on sunny days, there are dual landings on parallel runways at SFO. "On a clear day like today, airplanes can land side by side," he said.
However, in times of low visibility, such as on foggy days, the Federal Aviation Administration has prohibited such landings, and planes landed one by one, using a single runway.
"Essentially what you had was a single-file line," Yakel said.
Now, planes still won't be able to land side-by-side in inclement weather, but the FAA will allow staggered landings using both runways.
FAA spokesman Ian Gregor said that under the new protocol, an additional one to six aircraft should be able to land at SFO each hour on low-visibility days.
He said the new rules are "not a panacea" but that they should help alleviate some of the air traffic backup that occurs on rainy or foggy days.
"Every additional aircraft you can get in is a good thing," he said.
The change was made only after years of safety studies, Gregor said.
"We're always looking to see what we can do safely ... Before we make any change, we're going to study that extensively to make sure it's absolutely safe," he said.
The new landing rules were implemented on Sept. 30, and Yakel said it's too early to tell how much they will reduce flight delays on bad-weather days -- partly because the weather was so nice for much of October.
However, he said it should make a difference, as most delays at SFO are weather-related.