Airlines have canceled hundreds of flights as Tropical Storm Debby made landfall Monday.

Many cancellations affect flights to and from cities in Florida, and some affect routes to Atlanta.

On Monday, there are about 120 flights canceled at Hartsfield-Jackson International Airport, according to FlightAware.com. That includes more than 70 Delta Air Lines and Delta Connection flights. Atlanta-based Delta is the dominant carrier at Hartsfield-Jackson.

Dallas-based Southwest, the second-largest airline in Atlanta, canceled more than 20 flights at Hartsfield-Jackson on Monday, FlightAware data show.

The airports with the most flight cancellations as of Monday afternoon were Orlando, Tampa, Miami and Charlotte.

American Airlines, which has has hubs in Miami and Charlotte, reported the most flight cancellations nationally among U.S. airlines on Monday, with more than 375 cancellations, according to FlightAware. That’s after it canceled more than 740 flights on Sunday and more than 250 flights Saturday, FlightAware data show.

As of early Monday afternoon, American had canceled fewer than 10 of its mainline flights for the day in Atlanta. That’s partly because American makes up only about 2.3% of airline market share in Atlanta. Delta and its partners make up about 80% of the market share at Hartsfield-Jackson.

Delta has issued a travel waiver for Augusta and Savannah in Georgia; as well as Charleston, Columbia, Hilton Head and Myrtle Beach in South Carolina; Jacksonville and Tallahassee in Florida; and Wilmington, North Carolina.

Delta is allowing people who had flights booked to, from or through those cities for Monday, Tuesday or Wednesday this week to reschedule their flights to avoid the impact of the storm without paying a higher fare, subject to certain conditions.

The airline previously issued a travel waiver in effect through Monday for Fort Myers, Gainesville, Jacksonville, Key West, Sarasota, Tallahassee and Tampa in Florida, as well as Valdosta in Georgia, allowing similar flexibility.