Etihad Airways, UAE's national carrier,  has asked a German court for more time to continue code sharing with Air Berlin on 29 routes while it appeals a decision that will block it from operating the flights after January 15, it said.

A court in Brunswick last week said Etihad may not continue to jointly sell tickets for 29 routes operated by Air Berlin, in which Etihad owns a 29 percent stake, because they were not covered by the current air traffic rights agreement between Germany and the UAE.

The code shares are important for Air Berlin as it tries to return to profitability after years of losses. Such deals allow carriers to offer more destinations as part of their network, reaching more customers and thus helping to fill planes and boost revenues.

Etihad on Thursday said it wanted an appeals court to allow it to continue the code shares, which had previously been approved six times, until at least March 26 and that the Brunswick court had made errors in its interpretation of the agreement.

The carrier said the current bilateral air traffic rights agreement allows Etihad to fly to four destinations in Germany with its own aircraft, plus a further three in Germany via code-sharing, and that the agreement permits flights that go from these points beyond Germany.

"We are convinced that the conditions of the bilateral agreement are clear and we are confident that a correct review of our complaint will lead to the restoration of competition and choice on the German market," Jim Callaghan, Etihad Airways General Counsel, said in a statement.

Etihad has said the code shares were a key part of its case for investing in loss-making Air Berlin in 2012. While some analysts have queried whether Etihad will stand by Air Berlin, the Abu Dhabi-based airline has said it remains committed to Germany's second largest carrier.

But that has not stopped labour representatives at Air Berlin from writing to German Chancellor Angela Merkel to ask her to find a political answer to the dispute, German magazine Spiegel reported on its website.

The German transport ministry says it has repeatedly offered to hold talks with the UAE government over the bilateral agreement. - Reuters