German airline Air Berlin said it was calling on investors to stump up more cash by buying bonds as it unveiled a 2013 loss.

It said late on Sunday it was issuing a convertible bond worth 300 million euros ($415 million), to which its biggest shareholder Etihad Airways has subscribed, would make an exchange offer to bondholders with notes due in 2014 and 2015, plus issue new bonds with a volume of at least 150 million.

In addition, Etihad has agreed to extend a $255 million loan, of which Air Berlin has so far drawn $135 million, to the end of 2021 from the end of 2016.

Air Berlin, which built up debt after expanding too rapidly, had said last month it was in advanced talks over options that would have a substantial impact, sparking speculation over a possible move by Etihad to gain bigger control over the carrier.

But Air Berlin said on Sunday its recapitalisation would not change its ownership structure. Abu Dhabi-based Etihad owns 29.2 percent of Air Berlin while Turkey’s Sabanci family own a 12 percent stake. The European Union is looking into whether Etihad exercises more control than allowed under the region’s rules for airlines with a European operating licence.

Air Berlin slumped to a 2013 loss before interest and tax (EBIT) of 231.9 million euros, compared with a year-earlier profit of 70.2 million, citing an unexpectedly sluggish summer season due to high temperatures in central Europe and a difficult winter period.

The airline also named Marco Ciomperlik, currently its chief maintenance officer, to its management board to oversee its restructuring programme.

Air Berlin in November scrapped its aim of breaking even at the operating profit level in 2013 and warned it would only come close to consensus for a 40 million euro EBIT loss if it found additional sources of income.

Its net loss came to 315.5 million euros, compared with a year-earlier profit of 6.8 million euros, when it posted its first profit in five years in 2012 only by selling a majority stake in its frequent flyer programme to Etihad.

It said it would publish full financial results for 2013 on April 30.

Its net debt rose to 796 million euros from 770.2 million. Its total equity slumped to a negative 186.1 million euros from a positive 130.2 million in 2012, meaning its liabilities exceeded its assets.

(Reporting by Maria Sheahan; Editing by Andrew Roche and Victoria Bryan)

Photo Credit: A woman stands behind the exhibition stand of Air Berlin at the ITB tourism fair in Berlin. Tobias Schwarz / Reuters