An FAA review of a long-used arrival procedure at San Francisco International Airport (SFO) has deemed it non-compliant, prompting the agency to order immediate changes that cut the airport’s maximum arrival rate by nine flights per hour.

The change eliminates parallel approaches to Runways 28 Left and 28 Right that have been conducted for decades. Effective March 31, staggered approaches that used to be required in poor visibility are now standard in all weather.

“The FAA safety measure prohibits flights from making side-by-side approaches to SFO’s parallel east-west runways in clear weather when the pilots acknowledge having the other aircraft in sight,” the agency said.

The change was implemented as a major airfield construction project kicked off. But the FAA confirmed its move is not related to the work, which will see two of the airport’s four runways closed for about six months.

Before the project and FAA’s move, SFO’s maximum arrival rate was 54 aircraft per hour. Now, it is 36 per hour. The runway closures reduced the rate by nine arrivals, and FAA’s move cut another nine.

The FAA said it is “exploring ways to safely increase the airport arrival rate.”

The agency said the change resulted from a routine review of its policies and procedures. It declined to provide details.

A source with knowledge of the FAA’s decision said the change was prompted by an evaluation of airspace around SFO and an arriving aircraft’s ability to be established on the runway centerline far enough out to maintain safe separation. SFO’s Runways 28 Left and 28 Right are 750 ft. apart centerline—too close for unrestricted parallel operations. The change was not prompted by any specific incidents, the source added.

SFO handled 190,600 air carrier passenger and cargo landings in 2025, or about 520 per day, its monthly traffic report shows.

The airfield project will see Runway 1 Right resurfaced and improvements to adjacent taxiways, lighting, and markings.

SFO is operating all arrivals and departures on Runways 28 Left and 28 Right during the construction phase. Runway 1 Left, parallel to the repaving project, will be used as a taxiway to reduce ground congestion, the airport said.

The airport was projecting delays to about 15% of flights due to the construction. The FAA’s procedural changes could raise that to 25%, an airport spokesman said.

United Airlines, the airport’s dominant carrier, said the construction “may cause flight delays” and urges customers to monitor flight times in the United app. “Additionally, we are reviewing the FAA’s updated guidance to determine if we will need to make any changes to our flight schedule in the future,” the airline added.

The change prohibits clear-weather parallel arrival procedures used at SFO for decades. The FAA move does not affect other SFO capacity-enhancing protocols used in low-visibility conditions. These include combined Precision Runway Monitor/Simultaneous Offset Instrument Approach procedures introduced in 2005 and the Closely-Spaced Parallel Runways (CSPR) procedure rolled out in 2013.

—with reporting from Christine Boynton