Air Berlin and American Airlines have expanded their codeshare agreement to include selected flights within American's domestic route network.
Under the deal, Air Berlin passengers can access connecting flights from New York to Chicago, Cleveland, Pittsburgh and St Louis.
The codeshare also includes Key West and Jacksonville in Florida, as well as San Juan in Puerto Rico.
In addition, it includes connections from Los Angeles to five new domestic US destinations, including Sacramento and San José, California.
The two codeshare partners now offer a total of 33 destinations within the USA, Puerto Rico and the Bahamas with shared flight codes.