LOS ANGELES (Reuters) - Air traffic controllers lost radio contact with aircraft flying high-altitude routes in the western United States on Tuesday, disrupting thousands of flights heading in and out of southern California, authorities said.The Federal Aviation Administration said controllers in Los Angeles were directing high-altitude traffic when the communications outage occurred, but they continued to monitor the flights on radar.
"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," said FAA spokeswoman Laura Brown in Washington.
Some 800 flights 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.
The FAA said an alert was issued at 4:40 p.m. Pacific Daylight Time (7:40 p.m. EDT) after the radio problem was discovered and the national "ground stop" order was issued for all departing planes.
The ground stop was issued after high-altitude radio communications failed at the Los Angeles Air Route Traffic Control Center in Palmdale, California, about 60 miles north of Long Beach airport, officials 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 planes in flight at any moment.
En-route centers generally are responsible for airspace over a number of states.
A ground stop does not allow flights to depart but allows those that are already in the system to land, officials said.
Rob Wigington, a spokesman for Lindbergh Field in San Diego, said the FAA began allowing some flights to depart at about 8 p.m. PDT (11 p.m. EDT).
"All we've been told is that (an FAA communication) system is down," he said.
Officials at Los Angeles International Airport said about 50 flights were canceled or diverted to other airports as of about 7 p.m. PDT (10 p.m. EDT).
LAX spokeswoman Nancy Castles said airport officials could not yet determine how the stoppage would affect air traffic at one of the world's busiest airport.
"The backlog depends on how long it goes on," she said.
