(Updated 4:40 p.m.)

Southwest Airlines, now the second-largest carrier serving Hartsfield-Jackson International Airport after Delta Air Lines, has implemented its new “no show” policy for some passengers who don’t make their flight.

Passengers with nonrefundable fares who can’t make a flight and who don’t cancel or change it before the flight’s departure will lose the value of their ticket, and the remaining reservation will be canceled. If customers cancel their flight prior to departure, however, they will still be able to use the remaining value of their tickets to fly Southwest in the future without a change fee.

The policy affects customers with Wanna Get Away or DING! tickets, the airline said. Southwest first heralded the new policy last year and again in April.

The policy applies to reservations made or changed on or after May 10 for travel on or after Sept. 13. This policy does not apply to military fares, senior fares, or travel during certain irregular operations, including severe weather conditions, the airline said.

Southwest said customers who are traveling on a fully refundable flight that does not contain a Wanna Get Away or DING! fare will continue to have the option of either requesting a refund or holding funds for future travel.

A spokesman for Delta said passengers who show up within an hour of missing their scheduled flight will be re-accommodated at no additional charge. Customers who don't show up at all, however, will face additional fees.

“In all other situations, customers can redeem the original non-refundable ticket for future service plus a change fee and difference in fare up to one year from the original date of purchase,” spokesman Anthony Black said. Delta’s change fee is $200 for domestic flights and $300 for international flights..

Black said Delta will waive the additional charges in the case of death or serious illness with proper documentation.