A German court has ruled that Etihad Airways and Air Berlin can't continue code-sharing on some of their routes beyond mid-January.

Abu Dhabi-based Etihad holds 29.2 percent of Germany's second-biggest airline and their code-sharing provides important income for Air Berlin. However, the German government says some of the routes aren't covered by an aviation agreement with the United Arab Emirates. The problem involves 31 routes, with more than 50 others unaffected.

German authorities in October approved the disputed code-shares through Jan. 15, saying they were giving the companies time to find a solution.

Etihad sought a ruling from an administrative court in Braunschweig extending that permission to the end of the winter timetable in late March. However, the court said Wednesday it had rejected the application.