A dense fog advisory was in effect in Los Angeles and Orange counties Thursday morning.
Visibility will fall to a quarter-mile or less, due to a shallow but strong marine inversion. The dense fog was expected to lift or clear around 10 a.m.
In Los Angeles County, the fog could create hazardous driving conditions on Pacific Coast Highway and the 10, 105, 110, 405, 605 and 710 freeways. The dense fog advisory was expected to remain in effect until 8 a.m.
The fog also affected air travelers with a ground stoppage declared by the Federal Aviation Administration because of dense fog. The stoppage was lifted early Thursday morning at Los Angeles International Airport, but the weather was affecting flights originating at airports up to 1,500 miles away.
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The FAA Tier 2 ground stoppage, which began at 7 p.m. Wednesday, affecting flights from the Western United States and Northern Mexico, was lifted at 1 a.m., said Nancy Castles of Los Angeles World Airports, the city agency that operates LAX.
During the six-hour ground stoppage, LAX experienced 57 delayed and 13 cancelled arriving out of 250 scheduled arrivals in that period, Castles reported. There were also 31 delayed and 23 cancelled departing flights out of nearly 200 scheduled departures. Of the 57 delayed arrivals, 28 were diverted to Ontario Airport, Castles said. And of those 28 flights, 10 continued onto LAX while the passengers on the 18 other flights deplaned and were being bussed to LAX.
Although the fog prompted the FAA to initiate the stoppage, Castles said, flights that were already in the air before the stoppage was activated were allowed to land at LAX.
Two flights intended for John Wayne Airport in Orange County were also diverted to Ontario.
The decisions to divert to Ontario were left up to the pilots and most of the diverted flights were from commuter or regional airlines, Castles said.
Crystal Egger, Toni Guinyard and City News Service contributed to this report.