FairPlane, a German company specialised in passenger compensation claims, has taken legal action seeking to relocate Niki (Austria) (Vienna) bankruptcy proceedings from Germany to Austria, threatening to block the IAG International Airlines Group takeover, Kurier reported.

The company believes that the bankruptcy proceedings for the Vienna-based airline should be conducted by the Austrian Korneuburg regional court rather than by the Berlin Charlottenburg court which handles Air Berlin (1991)'s bankruptcy. FairPlane believes that if an Austrian court had jurisdiction over Niki bankruptcy proceedings, interests of passengers would have been better protected. It also claims that by separating the cases of Air Berlin and Niki, any conflicts of interest would have been avoided.

FairPlane currently represents Niki passengers in compensation proceedings covering some EUR1 million (USD1.2 million), Kurier reported.

"If the complaint before the Charlottenburg district court is successful, the sale of Niki to IAG would be at maximum risk," airberlin group Lucas Flöther administrator told Reuters.

The court announced it will issue its ruling on January 4 and underlined that for the time being all decisions taken in regard to the Niki bankruptcy are in force, Aero.de reported.

The jurisdiction of the court in Berlin was established in December based on the location of the majority of creditors.

Niki grounded all aircraft and suspended flight operations on December 14, 2017, after the European Commission blocked the proposed takeover of the carrier by Lufthansa Group on anti-competitive grounds. On December 29, IAG announced it would take over certain assets of Niki for EUR20 million (USD24 million) and would provide an additional EUR16.5 million in liquidity. The airline is set to be relaunched as an Austrian unit of Vueling Airlines, IAG's low-cost carrier.

Despite having its legal registration in Austria, prior to bankruptcy Niki operated chiefly out of German airports, including Düsseldorf, Berlin Tegel, and Hamburg Helmut Schmidt.