Southwest Airlines on Sept. 13 will add a no-show policy for nonrefundable fares not canceled or changed before departure.

In those scenarios, "all unused funds on the full itinerary will be lost," according to the airline. If a customer holding a nonrefundable fare does not use or cancel any portion of a ticketed itinerary, "the remaining reservation will be canceled." The new policy applies to reservations booked from May 10 for travel from Sept. 13. Southwest telegraphed the new policy last December.