Although you will not find it written anywhere, I have been advised by people in the training department that it means the following:
XTBN is - To Be Notified (no idea why they put an X before it).
You have not been allocated any duty on that day, however you can be called for duty as long as they notify you before 10PM the previous night.
Therefore it is not the same as Standby.
Last edited by Linerider; 10th Jun 2011 at 09:42.