What does the director of a radio show do?

Usually I drown out the listing of credits at the end of radio programs. But recently my ears have perked up when I heard the mention of a credit for directing. I.E.–at the end of Fresh Air and All Things Considered, they’ll say: “…and our program today was produced by blahblahblah, directed by blahblahblah, and engineered by blahblahblah.”

I’m pretty clear on what the producer & engineer do…but what the heck does the director of a radio program do? Most tasks that I can think of would seem to be taken care of by the producer. And I’m not talking about a radio station’s Program Director…that’s something totally different (not to confuse you).

Anyone here with radio industry experience that can shed some light on this for me?