BERLIN — A Berlin court says the insolvency administrator for bankrupt airline Air Berlin has sued its former largest shareholder, Gulf airline Etihad, for 2 billion euros ($2.26 billion) in damages.

The Berlin administrative court said Friday the suit alleges United Arab Emirates-based Etihad failed to live up to its financial obligations by withdrawing funding from the struggling airline.

The court says Etihad had been supporting Air Berlin and sent a so-called “comfort letter” in April 2017 assuring its continued backing for 18 months. But it then stopped the funding in August 2017, forcing Air Berlin to file for bankruptcy.

The suit asks for 500 million euros compensation and unspecified further damages, which the court estimated in total at some 2 billion euros.

Etihad has until the end of January to respond.

It did not immediately reply to an email seeking its response.