The Federal Aviation Administration says a brief power outage at a Southern California airport's air traffic control tower forced controllers to use portable radios to communicate with pilots and caused a number of flight delays.

Agency spokesman Ian Gregor says the outage Sunday at John Wayne Airport in Orange County lasted a little more than an hour.

Gregor says the tower had been running on an emergency generator since commercial power failed Friday. He says the backup generator stopped working at 11:42 a.m. Sunday, but the tower was able to revert back to commercial power by 1 p.m.

throughout the outage, controllers used radios to guide pilots through landings. Gregor says around 10 departing flights were delayed by a little over a half-hour.

Gregor says FAA technicians have determined what went wrong with the generator and are fixing it.