A power outage at a radar facility cut communications and disrupted air travel in and out of Southern California for more than an hour Tuesday, a Federal Aviation Administration spokesman said.
The outage at the Los Angeles Air Route Traffic Control Center was reported shortly after 5:30 p.m. and power was restored about 90 minutes later, said Allen Kenitzer, a regional spokesman for FAA.
"The generator kicked in, and backup power was re-established," Kenitzer said.
The cause of the problem was not known.
Some planes were able to land in the region during the outage because smaller air facilities, which were not affected, helped to communicate with them, Kenitzer said.
The radar center is located north of Los Angeles in the high desert at Palmdale. It handles flights on long-distance routes at 38,000 feet or higher in Southern California and parts of Arizona, Nevada and Utah.
Most regional flights were not affected, Kenitzer said.
Los Angeles International Airport, the world's fifth-busiest in terms of passenger volume, was "pretty much shut down" during the outage, spokesman Harold Johnson said.
He said he did not know how many delays occurred there, adding that a number of planes on lower-altitude routes were able to take off and land.
All flights departing San Diego's Lindbergh Field were halted at 5:42 p.m., said airport spokeswoman Diana Lucero. Arriving flights were unaffected by the power failure, she said.
Two Alaska Airlines flights headed to Southern California were diverted to Oakland International Airport, airport spokeswoman Rosemary Barnes said.
Planes also returned to San Francisco International Airport, where customs officials were on alert for the possibility of international flights being sent there.