The insolvency administrator for Air Berlin (1991) (Berlin Tegel) is preparing to sue Clearstream Banking AG, a Luxembourg-based subsidiary of capital markets firm Deutsche Börse, in an attempt to recover EUR497.8 million euros (USD592.8 million).

The complaint was about to be filed at the Higher Regional Court Frankfurt, the administrator said in a statement, as reported by the German business weekly Wirtschaftswoche and the Luxembourg Times.

Air Berlin filed for insolvency in August 2017 and ceased operations that October. As a shareholder of ordinary shares in Air Berlin plc, listed in the latter’s shareholder register in the United Kingdom, Clearstream Banking holds these shares in securities accounts for investors who have acquired entitlements to them, the administrator claimed.

But Air Berlin plc can no longer be recognised as a foreign company after Brexit as its administrative headquarters are in Germany, the administrator argued. It must be re-qualified as a company under German civil law, it said, which would make Clearstream a “personally liable partner of this company under civil law.”

The insolvency administrator intends to deploy the lawsuit to assert payment of amounts that are already outlined in the insolvency table. It also asked the court to clarify whether Clearstream is obliged to make further payments to bankruptcy creditors, which could amount to an additional EUR1 billion (USD1.19 billion).

Clearstream, a ​​settlement and custody unit of Deutsche Börse, told the Luxembourg Times on June 27 that it had looked into the claim as a precautionary measure and was seeking legal advice. However, it “considers any claims in this context to be unfounded. Clearstream will take all necessary and appropriate measures to defend itself against the claim.”