More then likely this is in anticipation of flowthru's beginning to move over to AA by spring or Summer. The company doesn't want to get caught without enough captains to cover the schedule for Spring/Summer flying because an overage of captains can be used to cover an underage of F/O's, wheras a shortage of captains grinds the schedule down.

There remains a possibility that the company will force all to flow, but more than likely those that pass will just mean another more junior goes. It's reasonable to assume 50-60% of the 244 will accept and that means 120-150 vacancies will occur over the next 6-8 months. First though, a bubble needs to be created to insure the process runs satisfactorily and that is the likely primary purpose of the vacancy bid, but additional factors may be involved as well.