If you can't apply through PMKeyS, you still need to notify your supervisor. They have the authority to approve your absence if you don't have access to PMKeyS.

This type of absence only applies if you’re not on any other type of short absence.

If you’re serving in the Navy, you’ll only be eligible for short absence travel time for more than 48 hours once in each financial year. You can still apply for absences shorter than 48 hours. 

If you need to appear on behalf of the ADF, you’ll be on duty and won’t need to take leave.