Air Berlin and Jat Airways have signed a codeshare agreement effective 1 August, subject to government approvals.
Under the accord, Air Berlin will place its code on the Serbian carrier's flights linking Belgrade with Berlin, Düsseldorf, Frankfurt and Stuttgart.
Jat will meanwhile place its code on Air Berlin's German domestic flights from Berlin, Düsseldorf, Frankfurt and Stuttgart, and on services from Berlin to the Scandinavian destinations of Copenhagen, Oslo and Stockholm.
The agreement is the latest in a flurry of codeshare agreements signed by airlines in which Etihad Airways has gained, or is in the process of gaining, significant financial stakes.
Two years ago, the Abu Dhabi-based carrier purchased a 29% stake in Air Berlin. Subsequently, it took a 40% stake in Air Seychelles, and smaller stakes in Virgin Australia and Aer Lingus. It is the process of finalising deals with Jat and India's Jet Airways.
Earlier this week, Air Berlin and Virgin Australia struck a deal under which the latter will from 1 August put its code on the German airline's daily Abu Dhabi flights from Berlin and Düsseldorf.
Air Berlin will codeshare on Virgin Australia's Abu Dhabi-Sydney and Phuket-Perth services, and on nine domestic routes.
In October 2012, Etihad, Air Berlin and Air France-KLM agreed a wide-ranging codeshare across their mutual networks, and last month Jet signed a codeshare with Air France-KLM to gain access to networks via Paris and Amsterdam. Air France-KLM is putting its code on services operated by Jet to destinations beyond Bengaluru, Delhi and Mumbai - such as Chennai, Kolkata and Hyderabad.