Do you need a DA Form 4187 for early report option to Korea when branch already authorized it on your orders??

Unless your assignment instructions authorizes Early Report you can not report early. Your Port Call section will not be able to reserve your flight greater than 10 days prior to report date. That is call your Availability Window. You can request up to 60 days early report via 4187 through your first O6 and submitted to HRC. Milper Message 13-117 outlines what you have to do. If it already in your assignment instructions, then you can report early. Just remember you last day of leave now becomes your report date on your DA 31.

Last I checked, you just get the early flight to Korea and sign in when you get there.