When George Mason first arrives in epidode 1, Nina refers to him as the district director. He is clearly subourdinate to Chapelle as he tells Jack he'll phone his boss to ask for the source of the data.

However, in episode 14, Tony tells Palmer that Chapelle is the district director, seemingly making him no more senior than Mason.

Additionally, in epidode 24 of season 2, Chapelle is on the phone to a more senior CTU agent who he identifies as District director Vaughn.

So who is the district director?