Leaving early

I'm trying to get out early today (Friday).  Leaving for my best friend's wedding in Nashville, about a four hour drive. For the first week of training most of the classes are tought by outside units or contractors which are not controlled by your squadron or flight commander. This means out is difficult to coordinate anything ahead of time and guarantee getting out early. Even the  schedule your flight commander gives you is subjective and is only a best guess estimate of when you will finish an activity. This is frustrating if you are trying to make solid plans and give people early notice.