About 100 flights were affected, either having to hold in the air, circle or stay on the ground at their departure points for a time, Federal Aviation Administration spokesman Donn Walker said. The outage was blamed on a power surge, he said.
Some departures from Los Angeles were also held but that was relatively quickly resolved, he said.
All radar, radios and telephones - essentially everything that controllers use to communicate with aircraft and other control facilities - was hit by the outage at 9:40 a.m.
Shortly after 11 a.m., Walker reported that most power was back on but enough equipment remained out that instrument approaches would not be possible. But good weather made instrument approaches unnecessary, he said.
Walker referred questions about the cause of the power surge to the city Department of Water and Power.