Publicis Groupe's Digitas is the incumbent on the U.S. media account. The shop will continue to handle other digital marketing tasks, according to people familiar with the matter.
Joanne Davis Consulting supported the agency search. Ms. Davis referred comment to the client.
Delta and Digitas did not immediately respond to a request for comment.
Delta spent $53 million in domestic measured media in 2015, which is about the same amount the company spent in 2014, according to Kantar Media.
The media agency review follows the airline's move last March to hire WPP's AKQA as its global digital agency of record in an effort to consolidate its separate mobile and dot-com accounts.
The company announced earlier this year that Delta President Ed Bastian will succeed Richard H. Anderson as CEO upon his retirement next month.