Possible Clues:

• 'Don't know yet,' on a schedule
• Itinerary abbr
• Sched. letters
• Letters in an incomplete schedule
• Letters in an unfilled sched. slot
• Abbr. for an unfilled slot
• Course list abbr
• Unscheduled, so far (Abbr.)
• ''We'll let you know,'' on a TV schedule
• Unhelpful sched. info