Airbus and a group of European airlines issued another warning that the European Commission faces sparking a trade war after extending its emission trading scheme to the global industry.

The plane maker had said that China has frozen some jet deals because of the scheme, and spearheaded a new warning to political leaders that more retaliation is imminent unless the European Union backs down and pursues a compromise.

International disquiet with the EU's unilateral imposition of charges for aircraft carbon dioxide has drawn widespread threats of retaliation, though to date the only hard-line response has been Airbus's recent claim that China suspended final approval of a $12 billion aircraft order placed last year.

"These threats are now real and being translated into concrete action," Airbus warned in a letter last week to EU leaders and German Chancellor Angela Merkel, co-signed by Deutsche Lufthansa AG, Air Berlin PLC and engine maker MTU.