Faced with the arrival of now Tropical Storm Irma, airlines serving the world’s busiest airport canceled  flights at Atlanta Hartsfield-Jackson International Airport. The issue is crosswinds. Atlanta’s five parallel runways are set to work with the prevailing east-west winds. Irma  packed  strong north-south winds when she hit the Georgia megahub Monday September 11. Aircraft can handle crosswinds—up to a point. In a prepared release Delta, Atlantas's (ATL) dominant airline, said:  “A slight crosswind is allowable and can be safely managed. But 40 mph (64kmh) or greater crosswinds, as the storm is expected to bring in Atlanta, may exceed allowable limits.” Pilots can land with below-limit crosswinds through a technique known as ”crabbing,” pointing the nose of the aircraft at an angle so it’s partially into the wind. Delta says wind shear could also pose a threat. The airline is acutely aware of what wind shear can do. Delta Flight 191 was a victim of the potentially deadly phenomenon back in 1985 at Dallas/Fort Worth International. One-hundred-and-thirty-seven died. Delta axed some 800 flights Monday. Southwest Airlines, Atlanta’s second largest airline, said it was cutting out all flying into the airport after 1 p.m. Eastern Time U.S. September 11. Carriers expect to resume flights Tuesday September 12. FlightAware reports there were 3,724 cancelled flights within, into or out of the United States September 11—a massive number. The tally should drop dramatically Tuesday,according to FlightAware, when 1,302 flights are canceled. Not only will Atlanta be coming back on line, airlines are set to re-start a slew of Florida operations, at least on a limited basis. The further south on the Florida Peninsula, as a rule, the quicker the flights re-start. Major Tampa player Southwest says you’ll have to wait till at least Wednesday September 13 to catch a Tampa flight. The focus for airlines as this unprecedented storm passes is safety; the watchword for airline passengers is patience. Read: Virgin Group founder Richard Branson calls for "Marshall Plan" to rebuild Caribbean.