Germany is blocking Abu Dhabi-based airline Etihad from selling tickets for some flights operated by partner Air Berlin, meaning the German airline could lose out on passengers it needs to fight its way back to profit.

Air Berlin, in which Etihad owns a 29% stake, said yesterday that 34 so-called codeshare flights with Etihad for its winter schedule had failed to win the approval of the German federal aviation authority (LBA), despite having been cleared in the past. The flights account for around 46,000 bookings.

Etihad and Air Berlin have in the past shared codes on flights to around 60 destinations, meaning their number of shared flights will more than halve. By putting its number on the German airline’s flights, Etihad can sell those connections to its customers and thus help loss-making Air Berlin to fill its planes.

Etihad is under investigation by German authorities over whether it exercises too much control over Air Berlin. For Air Berlin to maintain its European operating licence, it must be majority controlled by European investors.

The LBA checks codeshare deals every time airlines submit winter and summer schedules for flights to and from Germany.

A spokesman for the transport ministry said the 34 codeshare requests were rejected based on the traffic rights agreement that exists between the Germany and the UAE.

Under that agreement, UAE-based airlines may operate flights and codeshare services to four airports in Germany — Frankfurt, Duesseldorf, Munich and Hamburg — and they may operate codeshare services from those four airports to Berlin, Stuttgart and Nuremburg.

The two airlines have shared flight codes since 2012. Air Berlin said it could not understand the decision because the LBA had approved all six previous schedule proposals involving the codeshares.

“This decision does not reflect our legal position and will shake the trust of passengers in these flight connections, which have been available for a long time,” Air Berlin chief executive Wolfgang Prock-Schauer said in a statement.

Air Berlin made its first annual net profit in five years in 2012, but only after Etihad bought a majority stake in its frequent flyer programme.