Travelers should expect delays when they fly through San Francisco International Airport after the Federal Aviation Administration this week cut a third of its arrivals because of safety concerns and runway construction. A temporary runway project and permanent FAA rule change announced Tuesday me ans San Francisco’s airport will go from 54 plane arrivals an hour to 36 arrivals. It is not yet clear if any flights will be canceled. A deadly runway crash between Air Canada jet and a fire truck at New York’s LaGuardia Airport in March is the latest air-traffic safety calamity. But the aviation administration said the rule change is not triggered by broader safety concerns and only affects the San Francisco airport. Here’s what to know: Concerns involve parallel runways FAA spokesman Ian Gregor said officials decided that SFO’s longstanding practice of landing two planes at the same time on closely spaced parallel runways that are just 750 feet (228.60 meters) apart — along with congested airspace — was too dangerous. He could not say why the practice had been allowed. The San Francisco safety concerns are unique to that airport because of how close the parallel runways are and how complicated the airspace is with several surrounding airports. The San Francisco Bay Area is served by three major airports, including San José Mineta International Airport and Oakland San Francisco Bay Airport, and smaller ones. The airport operates on two sets of parallel runways. The north-south runways are out of commission for six months for a repaving project that is responsible for nine of the 18 flight-per-hour reductions. The rule change will affect the remaining nine flights. Long-term effect of delays is unclear Doug Yakel, an airport spokesman, said about 25% of arriving flights are expected to be delayed by 30 minutes or more. He said the airport is working with the FAA to improve arrival times but didn’t provide more specifics on whether flights might be canceled. United Airlines said it is reviewing the rule change to see if any changes need to be made to its flight schedule, a spokesperson said by email. United is the largest airline at SFO. Alaska Airlines, the second-largest carrier, said in an email that the situation was changing by the day, with 15 flights delayed out of SFO on Monday and none experiencing delays on Tuesday. The runway under construction is set to reopen on Oct. 2, which should alleviate some of the delays, Yakel said. ___ Associated Press writer Janie Har contributed reporting from San Francisco ...read more read less