SL SECURE: DOOR-TO-DOOR | SL TOP: DOOR-TO-DOOR SL FAST: DOOR-TO-AIRPORT | SL FLEX: DOOR-TO-AIRPORT   SL FLEX: DOOR-TO-AIRPORT SL FLEX is the way to send your products where the total transit time is less critical and consequently savings on freight costs can be achieved. Use of lower-deck capacity on scheduled quality carrier flights—on non-stop, direct flights, whenever possible. If the transportation from origin to destination involves a transfer, the longest permissible transit time at transfer point is 72 hours. Transit time: fastest available connection on same route for passenger transportation plus maximum of 72 hours.