UPDATE: Radio Problems Ground Many Flights in California Wed Sep 15, 2004 01:05 AM ET By Gina Keating LOS ANGELES (Reuters) - U.S. aviation authorities lifted an order grounding flights to southern California at 8 p.m. PDT (11 p.m. EDT) on Wednesday, more than three hours after air traffic controllers lost radio contact with high-altitude aircraft. Hundreds of flights were disrupted, but no safety incidents were reported during the communication outage, which began at about 4:40 p.m. PDT (7:40 p.m. EDT) at the Los Angeles Air Route Traffic Control Center in Palmdale, California, a Federal Aviation Administration official said. FAA officials did not explain the cause of the problem, Nancy Castles, spokeswoman for Los Angeles International Airport (LAX), said. "We can see the planes, we just don't have radio contact with them. We can't talk to them. It's not a problem with power, it's a problem with radio," FAA spokeswoman Laura Brown in Washington had said. The FAA turned over control of the Palmdale airspace, about a 200-mile radius, to other air traffic control facilities. Controllers at the Palmdale center direct traffic above 13,000 feet and there can be thousands of aircraft in flight at any moment. Palmdale is 39 miles northeast of Los Angeles. Castles said the airport began operating again at about 50 percent capacity and was expected to resume normal operations by 3 a.m. PDT (6 a.m. EDT) on Wednesday. About 400 flights were delayed, rerouted or canceled at LAX as a result of the outage, Castles said. The FAA said controllers in Palmdale were directing high-altitude traffic when the communications outage occurred, but they continued to monitor the flights on radar. Some 800 flights nationwide were affected, including passenger jets and private aircraft, but authorities said they all landed safely at their destinations or were diverted. Other planes were stopped from taking off from Los Angeles, San Diego and Las Vegas, while flights that had not yet departed for the region from other cities were grounded. President Bush was in Las Vegas on Wednesday on a campaign stop, but he left the city on Air Force One before the trouble started.