The final major changing of the guard at Chicago-based United Airlines became official today. United CEO Jeff Smisek was appointed chairman of the board of the world’s largest carrier, replacing Glenn Tilton, effective Dec. 31, 2012. Smisek will continue as United’s CEO as well.

Outgoing board chairman Tilton, who served as CEO of United prior to its merger with Continental Airlines in 2010, will remain a board member, though he is no longer part of United’s management team.

According to United, transition of the chairmanship at this point in time was part of the original 2010 merger agreement between United and Continental.