Communications equipment failed Tuesday at a regional air-traffic control center, shutting down all airline traffic within 250 miles of Memphis and causing a ripple effect across the country that grounded dozens of passenger and cargo flights.
The problem started when a major telephone line to the Memphis center went out at 12:35 p.m. EST. The Federal Aviation Administration said air-traffic control operations were back to normal about three hours later.
Air-traffic control centers in adjacent regions handled flights that were already in the air when the problem was discovered.
"The airspace was completely cleared by 1:30 (p.m.) Eastern time," FAA spokeswoman Kathleen Bergen said.
High-altitude flights through the region — which includes parts of Alabama, Mississippi, Arkansas, Missouri, Indiana, Kentucky and Tennessee — were discontinued while the equipment was being fixed.
"What we did is put a ground stop in place for any flight that would transition through that airspace. We held them on the ground wherever they were, whether it was Miami, Seattle, Los Angeles, Boston," Bergen said.
The FAA's action had a ripple effect in several airports.
David Magana, a spokesman at Dallas-Fort Worth International Airport, said about 50 flights had been delayed, but were in the process of departing Tuesday afternoon. About 50 other flights had to be canceled.
In Nashville, 12 Northwest Airlines flights were diverted, and 25 to 30 departures had been delayed one to two hours, airport spokeswoman Emily Richard said.
"This is not the way to start out our dream vacation of a lifetime," said Vernon Thompson, 64, waiting with his wife in Nashville to begin flying to New Zealand.
Bob Erickson, a traveling Fruit of the Loom underwear salesman from Bowling Green, Ky., said he was delayed five hours in Nashville on his way to New York. "What are you going to do?" a stoic Erickson said. "There's absolutely nothing you can do."
Disruptions affecting fewer flights were reported at many airports, including those serving Miami, Los Angeles, Phoenix, Pittsburgh, Tampa, Fla., and Raleigh and Charlotte, N.C. No major problems were reported at Atlanta's Hartsfield-Jackson Airport or Chicago's O'Hare and Midway airports, aviation officials said.
Memphis, with the headquarters of shipping giant FedEx Corp., is the world's busiest airport for cargo, handling 4.08 million tons of air freight in 2006. The Memphis airport also is a hub for Northwest Airlines.
FedEx had to divert only 11 incoming flights, which caused no major disruption in its delivery schedules, company spokeswoman Sandra Munoz said. The busiest part of the company's day is early in the morning.
Operations were back to normal by about 3:30 p.m., said Laura Brown, a spokeswoman for the FAA in Washington.
Brown said the outage affected the center's ability to talk to flights passing through its airspace and to other air traffic control facilities.
National Air Traffic Controllers union spokesman Doug Church called the outage a major safety problem. He said controllers had to use their personal cell phones to talk to other air-traffic control centers.
Brown would not comment on the union statement. She had no further details about the cause of the outage, including which telephone company operates the line that was lost.
The Memphis center is one of 20 air-traffic control facilities around the country. It handled almost 3 million flights last year, ranking it ninth among the 20.
"It's a big airspace, and there are lots of airplanes," Bergen said.