The U.S. Federal Aviation Administration said on Tuesday that it was imposing new safety restrictions at San Francisco International Airport that will limit some landings and lead to significant delays.

The 13th-busiest U.S. airport will experience delays due to a runway repaving project and the agency’s decision to prohibit flights from making side-by-side approaches to San Francisco’s parallel east-west runways in clear weather, the FAA said.

The two measures will reduce maximum rates from 54 flights per hour to 36, the FAA said, adding it does not plan to lift the restrictions once the runway repaving is completed.

The airport’s runway project will put the two north-south runways out of service for approximately six months.

San Francisco International Airport said in a statement that the changes would result in flight delays.

While the airport previously forecast about 15% of flights to be delayed by the runway project, it now expects the change to increase the potential for delays to about a quarter of arriving flights experiencing a delay of at least 30 minutes.

United Airlines accounts for about half of the passenger traffic at San Francisco, followed by Alaska Airlines with about 10%. United said the planned runway construction may cause flight delays.

The FAA said it is now requiring “staggered approaches, with one aircraft offset from the aircraft on the parallel runway.”

It said it had never allowed side-by-side approaches in bad weather, adding that it was exploring ways to safely increase the airport’s arrival rate and had taken a number of steps to reduce the chances of accidents due to visual separation issues.

The FAA said earlier this month it was tightening helicopter safety rules and would ​suspend use of visual separation between airplanes and helicopters ‌near major airports.

This follows the January 2025 mid-air collision between an American Airlines regional jet and an army helicopter that killed ​67 people.

The FAA cited two recent incidents in issuing ​the new rules, including a near miss involving an ⁠American Airlines flight and police helicopter near the San Antonio ​airport.

—

(Reporting by David Shepardson. Additional reporting by Allison Lampert in Montreal and Doyinsola Oladipo in New York; Editing by Mark Porter, Alexander Smith and Nick Zieminski)