The move follows the departure of Delta's marketing chief, Paul Matsen, last month.
A Delta spokeswoman couldn't immediately be reached and the agency spokespeople referred calls to the client.
Delta announced plans to ground Song, the money-losing though oft-lauded low-cost airline last October. At that time, Song's president, Joanne Smith, was named Delta VP-consumer marketing.
Song was best known for experiential flourishes that included flight attendant uniforms designed by Kate Spade, gourmet food and live TV and music service. Delta has said it plans to maintain the entertainment services and all-leather seats on Song's fleet of 50 or so Boeing 757s, which will be renovated and repainted, and to add those features to other Delta planes.
Delta, which is in the midst of bankruptcy proceedings, is now faced with the threat of a pilots' strike that could ultimately be fatal to the carrier. The pilots' union has already authorized a strike anytime after April 17. Hundreds of Delta pilots protested outside its Atlanta headquarters yesterday.
$40-$50 million media spend
Delta spends between $40 million and $50 million on measured media, according to executives familiar with the situation. SS&K's assignment is also expected to be heavy with nontraditional marketing.
The airline is also widely expected to drop the "Good Goes Around" tagline, introduced by Ogilvy.