Heavy fog caused flight delays at the Los Angeles International Airport (LAX) on Friday, the Federal Aviation Administration (FAA) said.

A check with several airlines serving LAX showed northbound flights were delayed by about 35 minutes at mid-morning, but southbound flights appeared to be on schedule, said the FAA.

Aircraft flying into San Francisco International Airport at mid-morning were delayed an average of 51 minutes, with many planes kept idling on the ground before departing for the Bay Area, the FAA said.

Air travel to and from the rest of the nation appeared to be moving smoothly, the FAA's Web site said.

The delays ended with the dissipation of the San Francisco Bay Area fog at noon.