JetBlue Airways and South African Airways want to expand their partnership to include code-sharing, starting this month.

The two carriers began interlining last May, without code-sharing. But in an application filed with the U.S. Transportation Department Feb. 2 (OST-2011-0017), the carriers disclosed that they signed a code-sharing agreement Jan. 24.

JetBlue is asking for DOT approval to place South African’s code on any JetBlue flights within the U.S., but identified 17 routes out of New York John F. Kennedy International Airport and four out of Washington Dulles International Airport.

Six of the New York city-pairs involve California or Florida markets, with others that include Boston, Charlotte, Chicago, Denver, Las Vegas, New Orleans, Phoenix and Washington. The Washington markets, in addition to New York, are Boston, Fort Lauderdale and Orlando.

South African already has DOT approval to serve 25 U.S. points beyond its U.S. gateways via a code-share with a U.S. partner.

JetBlue already code-shares out of New York and Boston with Lufthansa and with regional carrier Cape Air for some services in New England via Boston. But it had seemed content to maintain what it describes as “interline-plus” arrangements with other carriers, such as Aer Lingus, American Airlines and El Al and

with customers able to purchase a single itinerary in one transaction.

JetBlue calls the code-share agreement "another step forward in our partnership agreement," but othrewise is not commenting before DOT approval. South African declined comment.