A software problem disrupted radio communications at both Dallas-Fort Worth International Airport control towers early Monday, while fog, snow and wind threatened to hamper one of the busiest travel holidays of the year elsewhere. Flights in and out of Dallas were delayed by as much as an hour. Airport spokesman Ken Capps said in an e-mail that the problems was repaired at both towers after about 30 minutes. The outage, at about 7 a.m., affected both incoming and outgoing flights, according to the Federal Aviation Administration's Air Traffic Control System Command Center. The FAA declared a "ground stop," which cuts incoming flights by holding planes on the ground at their point of departure. In California, thick fog shut down runways at Burbank's Bob Hope Airport on Monday, and poor visibility prevented 12 planes from landing Sunday night for a Monday morning turnaround, leaving scores of passengers stranded, airport spokesman Victor Gill said. "It was quite severe," Gill said. "The runway is 400 feet from my office window, and I couldn't see it." The fog at the airport in Burbank, about 15 miles northwest of downtown Los Angeles, lifted by midmorning, but domino effects were expected to delay flights all day, Gill said. FAA spokesman Ian Gregor said Several flights also were diverted from Santa Monica Airport, and some flights were delayed at Los Angeles International Ai r p o r t a n d S a n Di e go International Airport, but things returned to normal later in the morning. In Atlanta, fog reduced visibility across the metro area to a quarter-mile and delayed flights by as much as 30 minutes during the morning rush. The FAA said flights bound for New York's LaGuardia International Airport and Chicago's O'Hare International Airport experienced delays of more than an hour. Winds at LaGuardia gusted to as much as 31 mph Monday, according to the National Weather Service. Me t e o ro l o g i s t s in the Midwest eyed weather fronts that could bring an onslaught of snow and cold that could snarl air traffic at O'Hare. Rain was expected to turn to wet snow Wednesday night, just before thousands board flights out of town or pass through one of the nation's busiest travel hubs. Weather and wind also were cited for delays in Newark, N.J., and Philadelphia.