Air Berlin and Etihad Airways have arranged to provide line maintenance for each other's aircraft in Abu Dhabi and Dusseldorf, following Etihad's decision last month to increase its shareholding in the German carrier to 29%.
The Middle Eastern airline started serving Dusseldorf with an Airbus A330-300 four times a week in December and plans to increase the frequency to daily flights from April.
Air Berlin Technik, which operates one of its two base maintenance facilities in the city, will provide the transit checks during the aircraft's turnaround.
In return, Etihad will undertake the respective checks for Air Berlin's aircraft in Abu Dhabi.
While Etihad also flies to Frankfurt and Munich, where Air Berlin Technik has line maintenance stations, its aircraft are currently supported by other MRO providers at these destinations.