According to a Delta statement, Irma’s anticipated general north-south wind direction relative to Atlanta’s east-west runway configuration is a major factor in decision to cancel flights. "As is the case at all airports, Atlanta’s five runways are aligned with the prevailing wind, which generally blows from the east or west. Aircraft are best suited to take off and land into the wind for better performance. When the wind direction is perpendicular to the runway, it’s called a crosswind and can make landing challenging and potentially unsafe. A slight crosswind is allowable and can be safely managed, but a 40 mph or greater crosswind, as the storm is expected to bring in Atlanta, may exceed allowable limits.latest forecast and hurricane projections, Delta teams in the airline’s Operations and Customer Center have decided to cancel about 800 flights Monday as Hurricane Irma is expected to bring to the Atlanta hub strong crosswinds that exceed operating limits on select mainline and regional aircraft."

Wind shear, lighting and other convective weather is also possible in the vicinity of Atlanta and may prompt additional flight cancellations.

Florida flights resuming
 Delta expects reports from airport authorities throughout the state Monday on the condition of runways, taxiways and terminal infrastructure, some of which sustained damage. Updates are expected throughout the morning and will determine Delta’s Florida restart.  Do check the status of your flight before leaving for the airport on the Fly Delta app or at delta.com. Delta recommends that customers transiting the airline's Atlanta hub Monday modify their itineraries around the city on delta.com.

Fee waivers
Delta has also combined and consolidated fee waivers through Sept. 17 for customers transiting three dozen destinations where flights will be affected by Irma, and created a new waiver for St. Thomas, St. Maarten and Turks and Caicos for customers ticketed through Oct. 31.

Today, Delta is operating  a humanitarian flight bringing in recovery supplies and flying out 150 U.S. citizens to Atlanta from hurricane-ravaged St. Thomas. 

Below is an updated airport-by-airport outlook for operations in the Caribbean, Florida and the southeastern U.S.