Additional information about which detailed type of SSM this is.
Legal values
NEW Inserts new flight leg information.
CNL Deletes all flight (leg) information in the given period matching the given ScheduleFlightDays / ScheduleFlightWeeks) (Nothing in the future will depend on the cancelled/deleted data.)
SKD Deletes all flight (leg) information in the given period. The end data is not mandatory. (Nothing in the future will depend on the cancelled/deleted data.)
