DM,

Once you start BI and get your fleet type go ahead and start the process there of telling them that you need the weekend off. Training is a priority but there are some things that everyone had to plan and commit for while swimming. There should be no pushback and they may tell you to talk with the fleet manager. They can do one of three, say no (shouldn't be since this is a must not want to situation). Tell you yes and scheduling whole build you that weekend off (most likely) or delay your training (good since you are already on property and building seniority).

You can even be proactive by starting online courseware early and etc...
Hope this helps.