(CNN) -- Atlanta's airport and airlines there continue to bear the brunt of this week's snowfall that paralyzed parts of the South as their employees struggle to get to work Thursday at the world's busiest airport.
Hartsfield-Jackson Atlanta International Airport had nearly 500 flight cancellations by noon ET, according to FlightAware.com.
Flight operations are usually back to nearly normal volume one or two days after such a weather event, said FlightAware.com's Mark Duell, barring any exceptional circumstances.
"The disruption to passengers is typically longer, but depends on the mix of passengers canceling their plans versus rebooking at a later date," he said via e-mail.
Cold temperatures and icy roads are preventing some airport and airline personnel from getting to the Atlanta airport. "Some Delta employees and other people (responsible for aircraft security sweeps and cleaning aircraft) are having trouble getting to work on time," said Delta Air Lines spokesman Morgan Durrant.
Delta canceled some 440 flights before noon Thursday, on top of about 1,500 canceled flights Wednesday. As temperatures warm up Thursday afternoon in Atlanta and the snow and ice melt, Durrant said he expects cancellations to drop.
Southwest Airlines, whose Southwest and AirTran airline brands have a large presence in Atlanta, pre-emptively canceled nearly 120 flights systemwide by midday Thursday.
"We are focused on resuming operations in Atlanta right now," said Southwest spokesman Dan Landson via e-mail. "Our operational planners are working with all (t)eams to ensure our operations can safely get underway."
Delta's travel waiver will remain in effect through Friday, Durrant said. That's because the airline still anticipates a small number of cancellations, mostly on Delta Connection regional flights, on Friday.