A vacancy is when the company fills pilot positions that have become available. They happen somewhere between every 2-6 months here. Basically in seniority order, everyone gets to pick their most desired position- if that position is Available- they get that position. At the end of that process anything left over is available to people yet to be hired. In the last vacancy, everything was filled with current pilots except NYC FOs.

So all new hires will go to NYC first- and in the next vacancy will be able to bid out to different bases if his/her seniority can hold a different base.