Communications between an air traffic control center in Memphis and an unknown number of airplanes flying through its territory were disrupted on Saturday, the Federal Aviation Administration said.
The outage began about 3:30 p.m. CDT when a car in Memphis struck a utility pole and severed a fiber-optic cable, FAA spokeswoman Kathleen Bergen said, adding air safety was not compromised.
Connections to about a dozen radio frequencies and data transmissions from radar towers were temporarily disrupted at the FAA's Memphis Center, which directs planes passing through a 250-mile radius from Memphis. A local representative of the traffic controllers' union said about a third of the center's frequencies were knocked out.
Some flights had to be rerouted to surrounding control centers, but the extent of delays was not immediately known, Bergen said. Communications were restored by 7 p.m. CDT.
Last September, the center lost all its communications and air traffic controllers had to scramble to route planes out of the seven-state area, which includes many cross-country flight paths. Some controllers resorted to using their personal cell phones to direct planes.
Bergen said Saturday's disruption was not as widespread and controllers used remaining frequencies to direct flights.
There is generally less air traffic on Saturday afternoons. September's outage occurred on a Tuesday and grounded dozens of passenger and cargo flights nationwide. Hundreds more flights were delayed.
The September outage prompted a review by the FAA and criticism from the air traffic controllers' union, which accused the agency of failing to fix problems with its newly installed communications system.
Saturday's outage showed that the system needs more backups, said Ron Carpenter, a Memphis controller and president of the local branch of the National Air Traffic Controllers Association.
"The biggest concern that we have is that we are no longer talking to airplanes," Carpenter said. "We can do without radar (in an emergency), but we need to talk to airplanes."
The FAA blamed last year's outage on the failure of a major AT&T phone line.
"They said when they fixed it the last time it was caused by (computer) card problem," Carpenter said. "Well, this is obviously a bigger problem."
Bergen said last year's outage was thoroughly investigated by the FAA's technological staff, but Saturday's problem was different in nature because it was caused by an accident.
"Any system that run 24/7, occasionally there's going to be an outage," she said. "Outages are very, very rare and we're very adept at handling them."