Irish budget carrier Ryanair is protesting a proposed Lufthansa acquisition of Air Berlin assets, following Air Berlin's filing for administration.
Ryanair is accusing the German government of a "conspiracy" to "carve up" Air Berlin and is submitting complaints to German competition regulator Bundeskartellamt as well as the European Commission.
The German government has agreed to guarantee a €150 million ($176 million) bridge loan to Air Berlin from bank KfW, after shareholder Etihad Airways ceased to continue funding the struggling airline.
Lufthansa and another, unnamed, airline are negotiating the acquisition of Air Berlin assets, says the government, and a decision is likely to be finalised over the next few weeks.
But Ryanair claims Air Berlin's insolvency is being "manufactured" in order to enable Lufthansa to take over the airline without taking on debts.
"Bearing in mind the scale of the market shares and the European implications involved, it is all the more important that the European Commission takes immediate and decisive action," it adds.